Architectures and methods for outputting different wavelength light out of waveguides

ABSTRACT

Architectures are provided for selectively outputting light for forming images, the light having different wavelengths and being outputted with low levels of crosstalk. In some embodiments, light is incoupled into a waveguide and deflected to propagate in different directions, depending on wavelength. The incoupled light then outcoupled by outcoupling optical elements that outcouple light based on the direction of propagation of the light. In some other embodiments, color filters are between a waveguide and outcoupling elements. The color filters limit the wavelengths of light that interact with and are outcoupled by the outcoupling elements. In yet other embodiments, a different waveguide is provided for each range of wavelengths to be outputted. Incoupling optical elements selectively incouple light of the appropriate range of wavelengths into a corresponding waveguide, from which the light is outcoupled.

PRIORITY CLAIM

This application is a continuation of U.S. application Ser. No.16/384,363 filed on Apr. 15, 2019, which is a divisional of U.S.application Ser. No. 14/869,537 filed on Sep. 29, 2015 (U.S. Pat. No.10,261,318), which claims the benefit of priority under 35 USC § 119(e)of U.S. Provisional Patent Application No. 62/057,165, filed on Sep. 29,2014, entitled “VIRTUAL AND AUGMENTED REALITY SYSTEMS AND METHODS,” theentirety of which is incorporated herein by reference.

INCORPORATION BY REFERENCE

This application incorporates by reference the entirety of each of thefollowing patent applications: U.S. application Ser. No. 14/331,218(attorney docket no. 20020.00); U.S. Provisional Application No.62/012,273 (attorney docket no. 30019.00); and U.S. ProvisionalApplication No. 62/005,807 (attorney docket no. 30016.00).

BACKGROUND Field

The present disclosure relates to virtual reality and augmented realityimaging and visualization systems.

Description of the Related Art

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, wherein digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR”, scenariotypically involves presentation of digital or virtual image informationwithout transparency to other actual real-world visual input; anaugmented reality, or “AR”, scenario typically involves presentation ofdigital or virtual image information as an augmentation to visualizationof the actual world around the user. For example, referring to FIG. 1,an augmented reality scene 1 is depicted wherein a user of an ARtechnology sees a real-world park-like setting 1100 featuring people,trees, buildings in the background, and a concrete platform 1120. Inaddition to these items, the user of the AR technology also perceivesthat he “sees” a robot statue 1110 standing upon the real-world platform1120, and a cartoon-like avatar character 1130 flying by which seems tobe a personification of a bumble bee, even though these elements 1130,1110 do not exist in the real world. Because the human visual perceptionsystem is complex, it is challenging to produce a VR or AR technologythat facilitates a comfortable, natural-feeling, rich presentation ofvirtual image elements amongst other virtual or real-world imageryelements.

Systems and methods disclosed herein address various challenges relatedto VR and AR technology.

SUMMARY Embodiment 1

An optical system comprising:

-   -   a waveguide comprising a first major surface and a second major        surface, the waveguide configured to propagate light by total        internal reflection between the first and the second major        surfaces;    -   an incoupling optical element configured to incouple incident        light into the waveguide at a first plurality of wavelengths        along a first direction and incouple incident light into the        waveguide at one or more second wavelengths along a second        direction, wherein incoupled light of the first plurality of        wavelengths propagate through the waveguide along the first        direction by total internal reflection and incoupled light of        the one or more second wavelengths propagate through the        waveguide along the second direction by total internal        reflection; and    -   first and second outcoupling optical elements configured to        outcouple the incoupled light out of the waveguide.

Embodiment 2

The optical system of Embodiment 1, wherein the incoupling opticalelement includes one or more diffractive optical elements.

Embodiment 3

The optical system of Embodiment 2, wherein the one or more diffractiveoptical elements comprises one or more of an analog surface reliefgrating (ASR), a binary surface relief structure (BSR), a hologram, anda switchable diffractive optical element.

Embodiment 4

The optical system of Embodiment 3, wherein the switchable diffractiveoptical element is a switchable Polymer Dispersed Liquid Crystal (PDLC)grating.

Embodiment 5

The optical system of any of Embodiments 1-4, further comprising:

-   -   a first wavelength selective reflector configured to reflect        incoupled light of the first plurality of wavelengths        propagating along the first direction, while passing light of        wavelengths other than the first plurality of wavelengths; and    -   a second wavelength selective reflector configured to reflect        incoupled light of the one or more second wavelengths        propagating along the second direction, while passing light of        wavelengths other than the one or more second wavelengths.

Embodiment 6

The optical system of Embodiment 5, further comprising:

-   -   a first absorber configured to absorb incoupled light passing        through the first wavelength selective reflector; and    -   a second absorber configured to absorb incoupled light passing        through the second wavelength selective reflector.

Embodiment 7

The optical system of Embodiment 5, wherein the first and secondwavelength selective reflectors are a dichroic filters.

Embodiment 8

The optical system of any of Embodiments 1-7, wherein the light at thefirst plurality of wavelengths includes red light and blue light.

Embodiment 9

The optical system of any of Embodiments 1-8, wherein the light of theone or more second wavelengths includes green light.

Embodiment 10

The optical system of any of Embodiments 1-9, further comprising:

-   -   first light distributing element configured to receive incoupled        light of the first plurality of wavelengths traveling along the        first direction and distribute the light of the first plurality        of wavelengths to the first outcoupling optical elements; and        second light distributing element configured to receive        incoupled light of the one or more second wavelengths traveling        along the second direction and distribute the light in the        second plurality of wavelengths to the second outcoupling        optical elements.

Embodiment 11

The optical system of Embodiment 10, wherein the first and the secondlight distributing elements comprise one or more diffractive opticalelements.

Embodiment 12

The optical system of Embodiment 11, wherein the one or more diffractiveoptical elements comprise one or more gratings.

Embodiment 13

The optical system of any of Embodiments 10-12, wherein the first lightdistributing element is configured to redirect light of the firstplurality of wavelengths to propagate within the waveguide along adirection different from a direction in which the second lightdistributing element is configured to redirect light of the secondplurality of wavelengths.

Embodiment 14

The optical system of any of Embodiments 10-13, wherein the first lightdistributing element is configured to redirect light of the firstplurality of wavelengths to propagate within the waveguide along thesecond direction, and wherein the second light distributing element isconfigured to redirect light of the second plurality of wavelengths topropagate within the waveguide along the first direction.

Embodiment 15

The optical system of any of Embodiments 10-14, wherein the first andsecond light distributing elements are orthogonal pupil expanders.

Embodiment 16

The optical system of any of Embodiments 1-15, wherein the firstoutcoupling optical element comprises one or more gratings configured tooutcouple light of the first plurality of wavelengths out of thewaveguide; and wherein the second outcoupling optical element comprisesone or more gratings configured to outcouple light of the one or moresecond wavelengths out of the waveguide.

Embodiment 17

The optical system of Embodiment 16, wherein the one or more gratings ofthe first outcoupling optical element are disposed on the first majorsurface of the waveguide and the one or more gratings of the secondoutcoupling optical element are disposed on the second major surface ofthe waveguide.

Embodiment 18

The optical system of Embodiment 16, wherein the one or more gratings ofthe first outcoupling optical element and the one or more gratings ofthe second outcoupling optical element are disposed on a same majorsurface of the waveguide.

Embodiment 19

The optical system of any of Embodiments 16-18, wherein the one or moregratings of the first outcoupling optical element comprises one or moreof an analog surface relief grating (ASR), a binary surface reliefstructure (BSR), a hologram, and a switchable diffractive opticalelement.

Embodiment 20

The optical system of Embodiment 19, wherein the switchable diffractiveoptical element comprises a switchable Polymer Dispersed Liquid Crystal(PDLC) grating.

Embodiment 21

An optical system comprising:

-   -   a plurality of stacked waveguides, each waveguide comprising a        first major surface and a second major surface, each waveguide        configured to propagate light by total internal reflection        between the first and the second major surfaces, each waveguide        further comprising:    -   incoupling optical element configured to incouple incident light        into the waveguide at a first plurality of wavelengths along a        first direction and incouple incident light into the waveguide        at one or more second wavelengths along a second direction; and    -   outcoupling optical element configured to outcouple the        incoupled light out of the waveguide.

Embodiment 22

The optical system of Embodiment 21, wherein each waveguide has anassociated depth plane, wherein each waveguide is configured to producean image appearing to originate from that waveguide's associated depthplane.

Embodiment 23

The optical system of any of Embodiments 21-22, wherein differentwaveguides have different associated depth planes.

Embodiment 24

The optical system of any of Embodiments 21-23, wherein the outcouplingoptical elements for different depth planes have different optical powerso as to provide different divergence of exiting light for each depthplane.

Embodiment 25

An optical system comprising:

-   -   a waveguide comprising a first major surface and a second major        surface;    -   an incoupling optical element configured to incouple incident        light into the waveguide;    -   a first wavelength selective filter on the first major surface,        the first wavelength selective filter having a first rearward        surface adjacent the first major surface and a first forward        surface opposite the first rearward surface, the first        wavelength selective filter configured to:    -   transmit incoupled light at a first plurality of wavelengths        through the first rearward surface of and reflect a portion of        the transmitted light at the first plurality of wavelengths from        the first forward surface; and    -   reflect incoupled light at other wavelengths; and    -   a first outcoupling optical element disposed on the first        wavelength selective filter, the first outcoupling optical        element configured to outcouple the incoupled light of the first        plurality of wavelengths transmitted through the first        wavelength selective filter.

Embodiment 26

The optical system of Embodiment 25, further comprising:

-   -   a second wavelength selective filter on the second major        surface, the second wavelength selective filter having a second        rearward surface adjacent the second major surface and a second        forward surface opposite the second rearward surface, the first        wavelength selective filter configured to:    -   transmit incoupled light at one or more second wavelengths        different from the first plurality of wavelengths through the        second rearward surface and reflect a portion of the transmitted        light at the one or more second wavelengths from the second        forward surface; and    -   reflect incoupled light at the first plurality of wavelengths;        and    -   a second outcoupling optical element disposed on the second        wavelength selective filter, the second outcoupling optical        element configured to outcouple the incoupled light at one or        more second wavelengths transmitted through the second        wavelength selective filter.

Embodiment 27

The optical system of Embodiment 26, wherein the first and the secondwavelength selective filters comprise dichroic filters.

Embodiment 28

The optical system of any of Embodiments 26-27, wherein the first andthe second wavelength selective filters are configured to transmit lightof the first plurality of wavelengths and the one or more secondwavelengths incident at angles between 0 degrees and 20 degrees withrespect to a normal to the corresponding first or the second majorsurface of the waveguide.

Embodiment 29

The optical system of any of Embodiments 26-28, wherein the light of theone or more second wavelengths includes green light.

Embodiment 30

The optical system of any of Embodiments 26-29, further comprising:

-   -   light distributing elements configured to:    -   receive incoupled light of the first plurality of wavelengths        and the one or more second wavelengths from the incoupling        optical element; and    -   distribute the light of the first plurality of wavelengths and        the one or more second wavelengths to the first and second        outcoupling optical elements.

Embodiment 31

The optical system of Embodiment 30, wherein the light distributingelements comprise one or more diffractive optical elements.

Embodiment 32

The optical system of any of Embodiments 30-31, wherein the lightdistributing elements are orthogonal pupil expanders.

Embodiment 33

The optical system of any of Embodiments 30-32, wherein a first portionof light at the first plurality of wavelengths is reflected from thefirst forward surface of the first wavelength selective filter and asecond portion of light at the first plurality of wavelengths isredirected by the light redistributing elements.

Embodiment 34

The optical system of Embodiment 33, wherein the first portion of lightat the first plurality of wavelengths is incident on the firstwavelength selective filter after being reflected from the second majorsurface, and wherein a portion of the first portion of light isredirected by the light redistributing elements.

Embodiment 35

The optical system of any of Embodiments 30-34, wherein a third portionof light at the one or more second wavelengths is reflected from thesecond forward surface of the second wavelength selective filter and afourth portion of light at the one or more second wavelengths isredirected by the light redistributing elements.

Embodiment 36

The optical system of Embodiment 35, wherein the third portion of lightat the one or more second wavelengths is incident on the secondwavelength selective filter after being reflected from the first majorsurface, and wherein a portion of the third portion of light isredirected by the light redistributing elements.

Embodiment 37

The optical system of any of Embodiments 26-36, wherein:

-   -   the first outcoupling element comprises one or more diffractive        optical elements; and    -   the second outcoupling element comprises one or more diffractive        optical elements.

Embodiment 38

The optical system of Embodiment 37, wherein the one or more diffractiveoptical elements of the first outcoupling optical element comprises oneor more of an analog surface relief grating (ASR), a binary surfacerelief structure (BSR), a hologram, and a switchable diffractive opticalelement.

Embodiment 39

The optical system of Embodiment 38, wherein the switchable diffractiveoptical element comprises a switchable Polymer Dispersed Liquid Crystal(PDLC) grating.

Embodiment 40

The optical system of Embodiment 37, wherein the one or more gratings ofthe second outcoupling optical element comprises one or more of ananalog surface relief grating (ASR), a binary surface relief structure(BSR), a hologram, and a switchable diffractive optical element.

Embodiment 41

The optical system of Embodiment 40, wherein the switchable diffractiveoptical element comprises a switchable Polymer Dispersed Liquid Crystal(PDLC) grating.

Embodiment 42

The optical system of any of Embodiments 25-41, wherein the incouplingoptical element includes one or more diffractive optical elements.

Embodiment 43

The optical system of Embodiment 42, wherein the one or more diffractiveoptical elements comprises one or more of an analog surface reliefgrating (ASR), a binary surface relief structure (BSR), a hologram, anda switchable diffractive optical element.

Embodiment 44

The optical system of Embodiment 43, wherein the switchable diffractiveoptical element is a switchable Polymer Dispersed Liquid Crystal (PDLC)grating.

Embodiment 45

The optical system of any of Embodiments 25-44, wherein the incouplingoptical element comprises a prism.

Embodiment 46

The optical system of any of Embodiments 25-46, wherein the light of thefirst plurality of wavelengths includes red light and blue light.

Embodiment 47

A optical system comprising:

-   -   a plurality of stacked waveguides, each waveguide comprising a        first major surface and a second major surface, each waveguide        further comprising:    -   an incoupling optical element configured to incouple incident        light into the waveguide;    -   a first wavelength selective filter on the first major surface,        the first wavelength selective filter having a first rearward        surface adjacent the first major surface and a first forward        surface opposite the first rearward surface, the first        wavelength selective filter configured to:    -   transmit incoupled light at a first plurality of wavelengths        through the first rearward surface of and reflect a portion of        the transmitted light at the first plurality of wavelengths from        the first forward surface; and    -   a first outcoupling optical element disposed on the first        wavelength selective filter, the first outcoupling optical        element configured to outcouple the incoupled light of the first        plurality of wavelengths transmitted through the first        wavelength selective filter.

Embodiment 48

The optical system of Embodiment 47, wherein each waveguide furthercomprises:

-   -   a second wavelength selective filter on the second major        surface, the second wavelength selective filter having a second        rearward surface adjacent the second major surface and a second        forward surface opposite the second rearward surface, the first        wavelength selective filter configured to:    -   transmit incoupled light at one or more second wavelengths        different from the first plurality of wavelengths through the        second rearward surface and reflect a portion of the transmitted        light at the one or more second wavelengths from the second        forward surface; and    -   a second outcoupling optical element disposed on the second        wavelength selective filter, the second outcoupling optical        element configured to outcouple the incoupled light at one or        more second wavelengths transmitted through the second        wavelength selective filter.

Embodiment 49

The optical system of any of Embodiments 47-48, wherein each waveguidehas an associated depth plane, wherein each waveguide is configured toproduce an image appearing to originate from that waveguide's associateddepth plane.

Embodiment 50

The optical system of any of Embodiments 47-49, wherein differentwaveguides have different associated depth planes.

Embodiment 51

The optical system of any of Embodiments 47-50, wherein the outcouplingoptical elements for different depth planes have different optical powerso as to provide different divergence of exiting light for each depthplane.

Embodiment 52

The optical system of any of Embodiments 48-51, wherein each waveguidefurther comprises a light redistributing element configured to:

-   -   receive a portion of light at the first plurality of wavelengths        and the one or more second wavelengths transmitted through the        first and the second wavelength selective filters; and    -   distribute the light of the first plurality of wavelengths and        the one or more second wavelengths to the first and second        outcoupling optical elements.

Embodiment 53

An optical system comprising:

-   -   a plurality of stacked waveguides, each waveguide comprising:    -   an incoupling optical element configured to selectively incouple        incident light into the waveguide based upon a property of the        incident light;    -   an outcoupling optical element configured to outcouple the light        incoupled into the waveguide.

Embodiment 54

The optical system of Embodiment 53, wherein the property of theincident light is wavelength.

Embodiment 55

The optical system of any of Embodiments 53-54, wherein the incouplingoptical element is a wavelength selective reflector.

Embodiment 56

The optical system of Embodiment 55, wherein the wavelength selectivereflector is a dichroic reflector.

Embodiment 57

The optical system of any of Embodiments 55-56, wherein each waveguidecomprises a wavelength selective reflector configured to reflect lightof a different range of wavelengths than the wavelength selectivereflector of another waveguide of the plurality of stacked waveguides.

Embodiment 58

The optical system of any of Embodiments 55-57, wherein each wavelengthselective reflector is configured to reflect light of a range ofwavelengths corresponding to a different color than the wavelengthselective reflector of other waveguides of the plurality of stackedwaveguides.

Embodiment 59

The optical system of any of Embodiments 53-58, wherein the plurality ofstacked waveguides comprises three waveguides, including a firstwaveguide configured to output red light, a second waveguide configuredto output green light, and a third waveguide configured to output bluelight.

Embodiment 60

The optical system of any of Embodiments 53-59, wherein the outcouplingoptical element is a diffractive optical element.

Embodiment 61

The optical system of Embodiment 60, wherein the diffractive opticalelement comprises one or more of an analog surface relief gratings(ASR), a binary surface relief structures (BSR), a hologram, and aswitchable diffractive optical element.

Embodiment 62

The optical system of Embodiment 61, wherein the switchable diffractiveoptical element comprises a switchable Polymer Dispersed Liquid Crystal(PDLC) grating.

Embodiment 63

The optical system of any of Embodiments 53-62, wherein each waveguidefurther comprises an angle-modifying optical element configured tomodify an angle of propagation of the incident light, such that theincident light propagates at a shallower angle to the waveguide surfaceafter impinging on the angle-modifying optical element.

Embodiment 64

The optical system of Embodiment 63, wherein the angle-modifying elementis configured to change focus of the incident light.

Embodiment 65

The optical system of Embodiment 63, wherein the angle-modifying opticalelement is a prism.

Embodiment 66

The optical system of Embodiment 63, wherein the angle-modifying opticalelement is a diffractive optical element.

Embodiment 67

The optical system of any of Embodiments 53-66, wherein each waveguidefurther comprises a light distributing element, wherein the incouplingoptical element is configured to direct light to the light distributingelement, wherein the light distributing element is configured to directlight to the outcoupling optical element.

Embodiment 68

The optical system of Embodiment 67, wherein the light distributingelement is an orthogonal pupil expander.

Embodiment 69

The optical system of any of Embodiments 67-68, wherein the lightdistributing element, the incoupling optical element, and theoutcoupling optical element are disposed on a surface of the waveguide.

Embodiment 70

The optical system of any of Embodiments 67-69, wherein the lightdistributing elements comprise one or more of analog surface reliefgratings (ASR), binary surface relief structures (BSR), a hologram, anda switchable diffractive optical element.

Embodiment 71

The optical system of Embodiment 70, wherein the switchable diffractiveoptical element comprises a switchable Polymer Dispersed Liquid Crystal(PDLC) grating.

Embodiment 72

An optical system comprising: multiple sets of stacked waveguides, eachset comprising a plurality of stacked waveguides, each waveguidecomprising:

-   -   an incoupling optical element configured to selectively incouple        incident light into the waveguide based upon a property of the        incident light; and    -   an outcoupling optical element configured to outcouple the light        incoupled into the waveguide.

Embodiment 73

The optical system of Embodiment 72, wherein each waveguide has anassociated depth plane, wherein each waveguide is configured to producean image appearing to originate from that waveguide's associated depthplane, and wherein waveguides of different sets of waveguides havedifferent associated depth planes.

Embodiment 74

The optical system of any of Embodiments 72-73, wherein waveguides ofeach set of stacked waveguides have the same associated depth plane.

Embodiment 75

The optical system of any of Embodiments 72-74, wherein the outcouplingoptical elements have optical power so as to provide a diverging lightbeam.

Embodiment 76

The optical system of any of Embodiments 72-75, wherein the outcouplingoptical elements for different depth planes have different optical powerso as to provide different divergence of exiting light for each depthplane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a user's view of augmented reality (AR) through an ARdevice.

FIG. 2 illustrates an example of wearable display system.

FIG. 3 illustrates a conventional display system for simulatingthree-dimensional imagery for a user.

FIG. 4 illustrates aspects of an approach for simulatingthree-dimensional imagery using multiple depth planes.

FIGS. 5A-5C illustrate relationships between radius of curvature andfocal radius.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user.

FIG. 7 shows an example of exit beams outputted by a waveguide.

FIG. 8 schematically illustrates an example of a stacked waveguideassembly in which each depth plane includes images formed using multipledifferent component colors.

FIG. 9A schematically illustrates an example of a top view of a displaydevice including a waveguide, an incoupling optical element, and anoutcoupling optical element.

FIG. 9B schematically illustrates an example of a cross-sectional viewof the display device depicted in FIG. 9A along the axis A-A′.

FIG. 9C illustrates an example of a dichroic wavelength selective filterand depicts the operation of the dichroic wavelength selective filter.

FIG. 10A schematically illustrates an example of a top view of a displaydevice including a waveguide, an incoupling optical element, wavelengthselective filters, and first and second outcoupling optical elements.

FIGS. 10B and 10C illustrate examples of a cross-sectional view of thedisplay device depicted in FIG. 10A along the axis A-A′.

FIG. 11A illustrates an example of a cross-sectional side view of aplurality of stacked waveguides that are each configured to output lightof a different wavelength or range of wavelengths.

FIG. 11B illustrates an example of a perspective view of the pluralityof stacked waveguides of FIG. 11A.

FIGS. 12A-12B illustrate examples of cross-sectional side views of awaveguide with an angle-modifying optical element to facilitate theincoupling of light into the waveguide.

FIG. 13 is a plot showing the expected impact of refractive index onfield of view.

The drawings are provided to illustrate certain example embodiments andare not intended to limit the scope of the disclosure. Like numeralsrefer to like parts throughout.

DETAILED DESCRIPTION

VR and AR experiences can be provided by display systems having displaysin which images corresponding to a plurality of depth planes areprovided to a viewer. The images may be different for each depth plane(e.g. provide slightly different presentations of a scene or object) andmay be separately focused by the viewer's eyes, thereby helping toprovide the user with depth cues based on the accommodation of the eyerequired to bring into focus different image features for the scenelocated on different depth plane and/or based on observing differentimage features on different depth planes being out of focus. Asdiscussed herein, such depth cues provide credible perceptions of depth.

In some configurations, a full color image may be formed for the variousdepth planes by overlaying component images that each have a particularcomponent color. For example, red, green, and blue images may each beoutputted to form each full color image. As a result, each depth planemay have multiple component color images associated with it. Asdisclosed herein, the component color images may be outputted usingwaveguides that incouple light containing image information, distributethe incoupled light across the waveguides, and then outcouple lighttowards a viewer.

Light may be incoupled to the waveguide using incoupling opticalelements, such as diffractive elements, and then outcoupled out of thewaveguide using outcoupling optical elements, which may also bediffractive elements. Conventionally, a pair of incoupling andoutcoupling optical elements may be used. Such an arrangement, however,can degrade image quality. For example, such optical elements typicallymost efficiently deflect a particular design wavelength and,undesirably, a full color image formed by red, green, and blue componentimages fed through such a system may exhibit significant cropping andmis-focusing depending on wavelength (e.g., cropping and mis-focusingmay occur for non-design wavelength channels). In addition, crosstalk,or ghosting may be caused by such the incoupling and outcoupling opticalelements. In some cases, a diffractive optical element optimized for onewavelength can cause ghost-like images to be formed when impinged uponby light of other wavelengths. For example, a diffractive opticalelement that is designed to place a green image on a depth plane 1 meterfrom the viewer may place blue and red images on depth planes closer orfarther than a meter. This crosstalk between depth planes can underminethe viewer's perception of depth and reduce image clarity.

In addition, color balance may be adversely impacted by the tendency ofincoupling and outcoupling optical elements such as diffractive opticalelements to deflect some amount of light even at wavelengths that theoptical elements are not specifically designed to deflect. Because afull color image is formed using multiple component color images, coloraccuracy in the full color image and the range of colors that areavailable may be dependent on the ability to precisely regulate theamount of light of the component colors that reaches the viewer.Crosstalk between the different component color images may beundesirable. For example, a full color image may be formed usingcomponent red, green, and blue images. A red component color image,formed using red-colored light, that also includes unintended greenlight or blue light is undesirable for, among other things, underminingthe ability to precisely regulate the amount of green or blue light thatmakes up the final full color image. This can reduce the color accuracyof the full color image and also reduce the range of colors that aregenerated, since the ability to precisely and finely regulateproportions of the different colors of light is diminished by thecrosstalk. Stated another way, the full color image may be of a higherquality when the component color images are each formed with light of a“pure” component color, rather than a “dirty” component color thatinclude a range of other unintended colors.

Advantageously, various embodiments disclosed herein provide low levelsof cross-talk and unintended outcoupling behavior.

In some embodiments, various architectures are provided for selectivelyoutputting light of different wavelengths with low levels of crosstalk.In some embodiments, light is incoupled into a waveguide and deflectedto propagate in different directions, depending on wavelength. Theincoupled light is then outcoupled by one or more outcoupling opticalelements that selectively outcouple light based on the direction ofpropagation of the light. In some embodiments, color filters areprovided between a waveguide and the one or more outcoupling elements onthe surface of the waveguide. The color filters limit the wavelengths oflight that interact with and are outcoupled by the one or moreoutcoupling elements. In yet other embodiments, a different waveguide isprovided for each range of wavelengths or colors to be outputted. One ormore incoupling optical elements selectively incouple light of theappropriate range of wavelengths into a corresponding waveguide, fromwhich the light is outcoupled.

In these various embodiments, as described herein, the waveguides mayform direct view display devices or near-eye display devices, with thewaveguides configured to receive input image information and generate anoutput image based on the input image information. These devices may bewearable and constitute eyewear. The input image information received bythe waveguides can be encoded in multiplexed light streams of differentwavelengths (e.g., red, green and blue light) which are incoupled intoone or more waveguides. The incoupled light can be outcoupled (oroutputted) from the waveguide by one or more outcoupling opticalelements. The one or more outcoupling optical elements can includediffractive structures, such as, for example, an analog surface reliefgrating (ASR), binary surface relief structures (BSR), VolumeHolographic Optical Elements (VHOE), Digital Surface Relief structuresand/or volume phase holographic material (e.g., holograms recorded involume phase holographic material), or a switchable diffractive opticalelement (e.g., Polymer Dispersed Liquid Crystal (PDLC) grating). It willbe appreciated that analog surface relief grating can combine multiplefunctions in a single structure. These structures may additively buildfunctionality (e.g., one functionality may be a selectively fordeflecting light of a particular wavelength or range of wavelengths, andanother functionality may be a selectivity for deflecting light ofanother wavelength or range of wavelengths) through successivefabrication steps (e.g., in which a structure with one functionality isbuilt on top of a structure with another functionality).

Various embodiments described herein can include one or more gratings(e.g., linear grooves) that are configured such that light propagatingalong a direction substantially parallel to the grating is notsufficiently deflected from its path such that it is coupled out of thewaveguide. In contrast, light propagating along a direction that is atan angle with respect to the grating (e.g., perpendicular to thegrooves), such that it impinges or strikes the grating, is diffracted atangles that do not satisfy the requirement for total internal reflection(TIR) and are thus coupled out of the waveguide. In some embodiments,the waveguide includes one or more incoupling optical elements that canredirect light at different directions that are compatible with theorientation of the corresponding diffractive structures.

Various embodiments described herein can include optical filters thattransmit specific wavelengths of light. The filters can limit thewavelengths of light that interact with or impinge on the one or moreoutcoupling optical elements, thereby reducing the likelihood of theoutcoupling of light of unintended wavelengths.

It will be appreciated that embodiments disclosed herein may provide oneor more of the following advantages. For example, as noted herein, theoutcoupling of light of unintended wavelengths may be reduced, therebyreducing the occurrence of ghosting, as discussed above. This reductionor elimination of ghosting can improve image clarity. In addition, thereduction in the outcoupling of light if unintended wavelengths canincrease the perceived color quality of images formed using the light.In some embodiments, the ability to specifically outcouple a desiredwavelength or range of wavelengths of light can provide images with ahigh degree of color accuracy and precision. In addition, the range ofcolors that may be displayed may be increased, since a high degree ofcontrol over the outcoupling of individual wavelengths of light mayprovide a high degree of control over the ultimate proportions ofparticular wavelengths of light in a final full color image. The abilityto precisely control proportions of different wavelengths of light canincrease the number of repeatable combination of component colorspossible, thereby increasing the number of colors (from mixtures of thecomponent colors) that may be displayed. In some embodiments, multiplewavelengths or colors of light may be outcoupled from the samewaveguide, which can have advantages for improving manufacturability andyield and reducing device costs by, for example, reducing the number ofparts utilized in a display system, thereby reducing the structural andelectrical complexity of the display system.

Embodiments disclosed herein may be implemented as display systemsgenerally. In some embodiments, the display systems take the form ofeyewear (e.g., they are wearable), which may advantageously provide amore immersive VR or AR experience. For example, displays containingwaveguides for displaying multiple depth planes, e.g. a stack ofwaveguides (one waveguide or set of waveguides for each depth plane),may be configured to be worn positioned in front of the eyes of a user,or viewer. In some embodiments, multiple waveguides, e.g. two stacks ofwaveguides, one for each eye of a viewer, may be utilized to providedifferent images to each eye.

FIG. 2 illustrates an example of wearable display system 80. The displaysystem 80 includes a display 62, and various mechanical and electronicmodules and systems to support the functioning of that display 62. Thedisplay 62 constitutes eyewear and may be coupled to a frame 64, whichis wearable by a display system user or viewer 60 and which isconfigured to position the display 62 in front of the eyes of the user60. In some embodiments, a speaker 66 is coupled to the frame 64 andpositioned adjacent the ear canal of the user 60 (in some embodiments,another speaker, not shown, is positioned adjacent the other ear canalof the user to provide for stereo/shapeable sound control). In someembodiments, the display system may also include one or more microphones67 or other devices to detect sound. In some embodiments, the microphoneis configured to allow the user to provide inputs or commands to thesystem 80 (e.g., the selection of voice menu commands, natural languagequestions, etc.) and/or may allow audio communication with other persons(e.g., with other users of similar display systems).

With continued reference to FIG. 2, the display 62 is operativelycoupled 68, such as by a wired lead or wireless connectivity, to a localdata processing module 70 which may be mounted in a variety ofconfigurations, such as fixedly attached to the frame 64, fixedlyattached to a helmet or hat worn by the user, embedded in headphones, orotherwise removably attached to the user 60 (e.g., in a backpack-styleconfiguration, in a belt-coupling style configuration). The localprocessing and data module 70 may comprise a hardware processor, as wellas digital memory, such as non-volatile memory (e.g., flash memory orhard disk drives), both of which may be utilized to assist in theprocessing, caching, and storage of data. The data include data a)captured from sensors (which may be, e.g., operatively coupled to theframe 64 or otherwise attached to the user 60), such as image capturedevices (such as cameras), microphones, inertial measurement units,accelerometers, compasses, GPS units, radio devices, and/or gyros;and/or b) acquired and/or processed using remote processing module 72and/or remote data repository 74, possibly for passage to the display 62after such processing or retrieval. The local processing and data module70 may be operatively coupled by communication links 76, 78, such as viaa wired or wireless communication links, to the remote processing module72 and remote data repository 74 such that these remote modules 72, 74are operatively coupled to each other and available as resources to thelocal processing and data module 70. In some embodiments, the locationprocessing and data module 70 may include one or more of the imagecapture devices, microphones, inertial measurement units,accelerometers, compasses, GPS units, radio devices, and/or gyros. Insome other embodiments, one or more of these sensors may be attached tothe frame 64, or may be stand alone structures that communicate with thelocation processing and data module 70 by wired or wirelesscommunication pathways.

With continued reference to FIG. 2, in some embodiments, the remoteprocessing module 72 may comprise one or more processors configured toanalyze and process data and/or image information. In some embodiments,the remote data repository 74 may comprise a digital data storagefacility, which may be available through the internet or othernetworking configuration in a “cloud” resource configuration. In someembodiments, all data is stored and all computations are performed inthe local processing and data module, allowing fully autonomous use froma remote module.

The perception of an image as being “three-dimensional” or “3-D” may beachieved by providing slightly different presentations of the image toeach eye of the viewer. FIG. 3 illustrates a conventional display systemfor simulating three-dimensional imagery for a user. Two distinct images5, 7—one for each eye 4, 6—are outputted to the user. The images 5, 7are spaced from the eyes 4, 6 by a distance 10 along an optical orz-axis parallel to the line of sight of the viewer. The images 5, 7 areflat and the eyes 4, 6 may focus on the images by assuming a singleaccommodated state. Such systems rely on the human visual system tocombine the images 5, 7 to provide a perception of depth for thecombined image.

It will be appreciated, however, that the human visual system is morecomplicated and providing a realistic perception of depth is morechallenging. For example, many viewers of conventional “3-D” displaysystems find such systems to be uncomfortable or may not perceive asense of depth at all. Without being limited by theory, it is believedthat viewers of an object may perceive the object as being“three-dimensional” due to a combination of vergence and accommodation.Vergence movements (i.e., rolling movements of the pupils toward or awayfrom each other to converge the lines of sight of the eyes to fixateupon an object) of the two eyes relative to each other are closelyassociated with focusing (or “accommodation”) of the lenses of the eyes.Under normal conditions, changing the focus of the lenses of the eyes,or accommodating the eyes, to change focus from one object to anotherobject at a different distance will automatically cause a matchingchange in vergence to the same distance, under a relationship known asthe “accommodation-vergence reflex.” Likewise, a change in vergence willtrigger a matching change in accommodation, under normal conditions. Asnoted herein, many stereoscopic or “3-D” display systems display a sceneusing slightly different presentations (and, so, slightly differentimages) to each eye such that a three-dimensional perspective isperceived by the human visual system. Such systems are uncomfortable formany viewers, however, since they, among other things, simply providedifferent presentations of a scene, but with the eyes viewing all theimage information at a single accommodated state, and work against the“accommodation-vergence reflex.” Display systems that provide a bettermatch between accommodation and vergence may form more realistic andcomfortable simulations of three-dimensional imagery.

FIG. 4 illustrates aspects of an approach for simulatingthree-dimensional imagery using multiple depth planes. With reference toFIG. 4, objects at various distances from eyes 4, 6 on the z-axis areaccommodated by the eyes 4, 6 so that those objects are in focus. Theeyes (4 and 6) assume particular accommodated states to bring into focusobjects at different distances along the z-axis. Consequently, aparticular accommodated state may be said to be associated with aparticular one of depth planes 14, with has an associated focaldistance, such that objects or parts of objects in a particular depthplane are in focus when the eye is in the accommodated state for thatdepth plane. In some embodiments, three-dimensional imagery may besimulated by providing different presentations of an image for each ofthe eyes 4, 6, and also by providing different presentations of theimage corresponding to each of the depth planes. While shown as beingseparate for clarity of illustration, it will be appreciated that thefields of view of the eyes 4, 6 may overlap, for example, as distancealong the z-axis increases. Additionally, while shown as flat for easeof illustration, it will be appreciated that the contours of a depthplane may be curved in physical space, such that all features in a depthplane are in focus with the eye in a particular accommodated state.

The distance between an object and the eye 4 or 6 can also change theamount of divergence of light from that object, as viewed by that eye.FIGS. 5A-5C illustrates relationships between distance and thedivergence of light rays. The distance between the object and the eye 4is represented by, in order of decreasing distance, R1, R2, and R3. Asshown in FIGS. 5A-5C, the light rays become more divergent as distanceto the object decreases. As distance increases, the light rays becomemore collimated. Stated another way, it may be said that the light fieldproduced by a point (the object or a part of the object) has a sphericalwavefront curvature, which is a function of how far away the point isfrom the eye of the user. The curvature increases with decreasingdistance between the object and the eye 4. Consequently, at differentdepth planes, the degree of divergence of light rays is also different,with the degree of divergence increasing with decreasing distancebetween depth planes and the viewer's eye 4. While only a single eye 4is illustrated for clarity of illustration in FIGS. 5A-5C and otherfigures herein, it will be appreciated that the discussions regardingeye 4 may be applied to both eyes 4 and 6 of a viewer.

Without being limited by theory, it is believed that the human eyetypically can interpret a finite number of depth planes to provide depthperception. Consequently, a highly believable simulation of perceiveddepth may be achieved by providing, to the eye, different presentationsof an image corresponding to each of these limited number of depthplanes. The different presentations may be separately focused by theviewer's eyes, thereby helping to provide the user with depth cues basedon the accommodation of the eye required to bring into focus differentimage features for the scene located on different depth plane and/orbased on observing different image features on different depth planesbeing out of focus.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user. A display system 1000 includes a stack ofwaveguides, or stacked waveguide assembly, 178 that may be utilized toprovide three-dimensional perception to the eye/brain using a pluralityof waveguides 182, 184, 186, 188, 190. In some embodiments, the displaysystem 1000 is the system 80 of FIG. 2, with FIG. 6 schematicallyshowing some parts of that system 80 in greater detail. For example, thewaveguide assembly 178 may be part of the display 62 of FIG. 2.

With continued reference to FIG. 6, the waveguide assembly 178 may alsoinclude a plurality of features 198, 196, 194, 192 between thewaveguides. In some embodiments, the features 198, 196, 194, 192 may belens. The waveguides 182, 184, 186, 188, 190 and/or the plurality oflenses 198, 196, 194, 192 may be configured to send image information tothe eye with various levels of wavefront curvature or light raydivergence. Each waveguide level may be associated with a particulardepth plane and may be configured to output image informationcorresponding to that depth plane. Image injection devices 200, 202,204, 206, 208 may function as a source of light for the waveguides andmay be utilized to inject image information into the waveguides 182,184, 186, 188, 190, each of which may be configured, as describedherein, to distribute incoming light across each respective waveguide,for output toward the eye 4. Light exits an output surface 300, 302,304, 306, 308 of the image injection devices 200, 202, 204, 206, 208 andis injected into a corresponding input surface 382, 384, 386, 388, 390of the waveguides 182, 184, 186, 188, 190. In some embodiments, theinput surfaces 382, 384, 386, 388, 390 may be an edge of a correspondingwaveguide, or may be part of a major surface of the correspondingwaveguide (that is, one of the waveguide surfaces directly facing theworld 144 or the viewer's eye 4). In some embodiments, a single beam oflight (e.g. a collimated beam) may be injected into each waveguide tooutput an entire field of cloned collimated beams that are directedtoward the eye 4 at particular angles (and amounts of divergence)corresponding to the depth plane associated with a particular waveguide.In some embodiments, a single one of the image injection devices 200,202, 204, 206, 208 may be associated with and inject light into aplurality (e.g., three) of the waveguides 182, 184, 186, 188, 190.

In some embodiments, the image injection devices 200, 202, 204, 206, 208are discrete displays that each produce image information for injectioninto a corresponding waveguide 182, 184, 186, 188, 190, respectively. Insome other embodiments, the image injection devices 200, 202, 204, 206,208 are the output ends of a single multiplexed display which may, e.g.,pipe image information via one or more optical conduits (such as fiberoptic cables) to each of the image injection devices 200, 202, 204, 206,208. It will be appreciated that the image information provided by theimage injection devices 200, 202, 204, 206, 208 may include light ofdifferent wavelengths, or colors (e.g., different component colors, asdiscussed herein).

A controller 210 controls the operation of the stacked waveguideassembly 178 and the image injection devices 200, 202, 204, 206, 208. Insome embodiments, the controller 210 is part of the local dataprocessing module 70. The controller 210 includes programming (e.g.,instructions in a non-transitory medium) that regulates the timing andprovision of image information to the waveguides 182, 184, 186, 188, 190according to, e.g., any of the various schemes disclosed herein. In someembodiments, the controller may be a single integral device, or adistributed system connected by wired or wireless communicationchannels. The controller 210 may be part of the processing modules 70 or72 (FIG. 1) in some embodiments.

With continued reference to FIG. 6, the waveguides 182, 184, 186, 188,190 may be configured to propagate light within each respectivewaveguide by total internal reflection (TIR). The waveguides 182, 184,186, 188, 190 may each be planar or have another shape (e.g., curved),with major top and bottom surfaces and edges extending between thosemajor top and bottom surfaces. In the illustrated configuration, thewaveguides 182, 184, 186, 188, 190 may each include one or moreoutcoupling optical elements 282, 284, 286, 288, 290 that are configuredto extract light out of a waveguide by redirecting the light,propagating within each respective waveguide, out of the waveguide tooutput image information to the eye 4. Extracted light may also bereferred to as outcoupled light and the one or more outcoupling opticalelements light may also be referred to light extracting opticalelements. An extracted beam of light is outputted by the waveguide atlocations at which the light propagating in the waveguide strikes alight extracting optical element. Some or all of the one or moreoutcoupling optical elements 282, 284, 286, 288, 290 may, for example,can be one or more gratings, including diffractive optical features, asdiscussed further herein. While illustrated disposed at the bottom majorsurfaces of the waveguides 182, 184, 186, 188, 190 for ease ofdescription and drawing clarity, in some embodiments, the one or moreoutcoupling optical elements 282, 284, 286, 288, 290 may be disposed atthe top and/or bottom major surfaces, and/or may be disposed directly inthe volume of the waveguides 182, 184, 186, 188, 190, as discussedfurther herein. In some embodiments, the one or more outcoupling opticalelements 282, 284, 286, 288, 290 may be formed in a layer of materialthat is attached to a transparent substrate to form the waveguides 182,184, 186, 188, 190. In some other embodiments, the waveguides 182, 184,186, 188, 190 may be a monolithic piece of material and the one or moreoutcoupling optical elements 282, 284, 286, 288, 290 may be formed on asurface and/or in the interior of that piece of material.

With continued reference to FIG. 6, as discussed herein, each waveguide182, 184, 186, 188, 190 is configured to output light to form an imagecorresponding to a particular depth plane. For example, the waveguide182 nearest the eye may be configured to deliver collimated light, asinjected into such waveguide 182, to the eye 4. The collimated light maybe representative of the optical infinity focal plane. The nextwaveguide up 184 may be configured to send out collimated light whichpasses through the first lens 192 (e.g., a negative lens) before it canreach the eye 4; such first lens 192 may be configured to create aslight convex wavefront curvature so that the eye/brain interprets lightcoming from that next waveguide up 184 as coming from a first focalplane closer inward toward the eye 4 from optical infinity. Similarly,the third up waveguide 186 passes its output light through both thefirst 192 and second 194 lenses before reaching the eye 4; the combinedoptical power of the first 192 and second 194 lenses may be configuredto create another incremental amount of wavefront curvature so that theeye/brain interprets light coming from the third waveguide 186 as comingfrom a second focal plane that is even closer inward toward the personfrom optical infinity than was light from the next waveguide up 184.Other ways of producing these perceived colors may be possible.

The other waveguide layers 188, 190 and lenses 196, 198 are similarlyconfigured, with the highest waveguide 190 in the stack sending itsoutput through all of the lenses between it and the eye for an aggregatefocal power representative of the closest focal plane to the person. Tocompensate for the stack of lenses 198, 196, 194, 192 whenviewing/interpreting light coming from the world 144 on the other sideof the stacked waveguide assembly 178, a compensating lens layer 180 maybe disposed at the top of the stack to compensate for the aggregatepower of the lens stack 198, 196, 194, 192 below. Such a configurationprovides as many perceived focal planes as there are availablewaveguide/lens pairings. Both the one or more outcoupling opticalelements of the waveguides and the focusing aspects of the lenses may bestatic (i.e., not dynamic or electro-active). In some alternativeembodiments, either or both may be dynamic using electro-activefeatures.

In some embodiments, two or more of the waveguides 182, 184, 186, 188,190 may have the same associated depth plane. For example, multiplewaveguides 182, 184, 186, 188, 190 may be configured to output imagesset to the same depth plane, or multiple subsets of the waveguides 182,184, 186, 188, 190 may be configured to output images set to the sameplurality of depth planes, with one set for each depth plane. This canprovide advantages for forming a tiled image to provide an expandedfield of view at those depth planes.

With continued reference to FIG. 6, the one or more outcoupling opticalelements 282, 284, 286, 288, 290 may be configured to both redirectlight out of their respective waveguides and to output this light withthe appropriate amount of divergence or collimation for a particulardepth plane associated with the waveguide. As a result, waveguideshaving different associated depth planes may have differentconfigurations of one or more outcoupling optical elements 282, 284,286, 288, 290, which output light with a different amount of divergencedepending on the associated depth plane. In some embodiments, thefeatures 198, 196, 194, 192 may not be lenses; rather, they may simplybe spacers (e.g., cladding layers and/or structures for forming airgaps).

In some embodiments, the one or more outcoupling optical elements 282,284, 286, 288, 290 are diffractive features that form a diffractionpattern, or “diffractive optical element” (also referred to herein as a“DOE”). Preferably, the DOE's have a sufficiently low diffractionefficiency so that only a portion of the light of the beam is deflectedaway toward the eye 4 with each intersection of the DOE, while the restcontinues to move through a waveguide via total internal reflection. Thelight carrying the image information is thus divided into a number ofrelated exit beams that exit the waveguide at a multiplicity oflocations and the result is a fairly uniform pattern of exit emissiontoward the eye 4 for this particular collimated beam bouncing aroundwithin a waveguide.

In some embodiments, one or more DOEs may be switchable between “on”states in which they actively diffract, and “off” states in which theydo not significantly diffract. For instance, a switchable DOE maycomprise a layer of polymer dispersed liquid crystal, in whichmicrodroplets comprise a diffraction pattern in a host medium, and therefractive index of the microdroplets can be switched to substantiallymatch the refractive index of the host material (in which case thepattern does not appreciably diffract incident light) or themicrodroplet can be switched to an index that does not match that of thehost medium (in which case the pattern actively diffracts incidentlight).

FIG. 7 shows an example of exit beams outputted by a waveguide. Onewaveguide is illustrated, but it will be appreciated that otherwaveguides in the waveguide assembly 178 may function similarly, wherethe waveguide assembly 178 includes multiple waveguides. Light 400 isinjected into the waveguide 182 at the input edge 382 of the waveguide182 and propagates within the waveguide 182 by TIR. At points where thelight 400 impinges on the DOE 282, a portion of the light exits thewaveguide as exit beams 402. The exit beams 402 are illustrated assubstantially parallel but, as discussed herein, they may also beredirected to propagate to the eye 4 at an angle (e.g., formingdivergent exit beams), depending on the depth plane associated with thewaveguide 182. It will be appreciated that substantially parallel exitbeams may be indicative of a waveguide with one or more outcouplingoptical elements that outcouple light to form images that appear to beset on a depth plane at a large distance (e.g., optical infinity) fromthe eye 4. Other waveguides or other sets of outcoupling opticalelements may output an exit beam pattern that is more divergent, whichwould require the eye 4 to accommodate to a closer distance to bring itinto focus on the retina and would be interpreted by the brain as lightfrom a distance closer to the eye 4 than optical infinity.

FIG. 8 schematically illustrates an example of a stacked waveguideassembly in which each depth plane includes images formed using multipledifferent component colors. In some embodiments, a full color image maybe formed at each depth plane by overlaying images in each of thecomponent colors, e.g., three or more component colors. The illustratedembodiment shows depth planes 14 a-14 f, although more or fewer depthsare also contemplated. Each depth plane may have three component colorimages associated with it: a first image of a first color, G; a secondimage of a second color, R; and a third image of a third color, B.Different depth planes are indicated in the figure by different numbersfor diopters following the letters G, R, and B. Just as examples, thenumbers following each of these letters indicate diopters (1/m), ordistance of the depth plane from a viewer, and each box in the figuresrepresents an individual component color image.

In some embodiments, light of each component color may be outputted by asingle dedicated waveguide and, consequently, each depth plane may havemultiple waveguides associated with it. In such embodiments, each box inthe figures including the letters G, R, or B may be understood torepresent an individual waveguide, and three waveguides may be providedper depth plane where three component color images are provided perdepth plane. While the waveguides associated with each depth plane areshown adjacent to one another in this schematic drawing for ease ofdescription, it will be appreciated that, in a physical device, thewaveguides may all be arranged in a stack with one waveguide per level.In some other embodiments, multiple component colors may be outputted bythe same waveguide, such that, e.g., only a single waveguide may beprovided per depth plane.

With continued reference to FIG. 8, in some embodiments, G is the colorgreen, R is the color red, and B is the color blue. In some otherembodiments, other colors, including magenta and cyan, may be used inaddition to or may replace one or more of red, green, or blue.

It will be appreciated that references to a given color of lightthroughout this disclosure will be understood to encompass light of oneor more wavelengths within a range of wavelengths of light that areperceived by a viewer as being of that given color. For example, redlight may include light of one or more wavelengths in the range of about620-780 nm, green light may include light of one or more wavelengths inthe range of about 492-577 nm, and blue light may include light of oneor more wavelengths in the range of about 435-493 nm.

With reference now to FIG. 9A, an example of a top view of a displaydevice 900 including a waveguide 905, an incoupling optical element 907and one or more outcoupling optical elements 909 a/909 b isschematically illustrated. The waveguide 905 can be planar, having afirst major surface 905 a, a second major surface 905 b opposite thefirst major surface 905 b and edges extending between those first andthe second major surfaces 905 a and 905 b. In such embodiments, thefirst and the second major surfaces 905 a and 905 b can extend in thex-y plane and a surface normal that intersects the first and the secondmajor surfaces 905 and 905 b can be oriented along the z-axis. Thewaveguide 905 can comprise an optical grade material that is configuredto be transmissive to wavelengths in the visible spectrum or wavelengthscorresponding to the component colors to be outputted by the waveguide905. In various embodiments, the waveguides disclose herein, includingthe waveguide 905 can be monolithic piece of material. For example, thefirst and the second major surfaces 905 a and 905 b and the spacebetween the two major surfaces 905 a and 905 b comprise the samematerial. In some embodiments, the waveguides may include multiplelayers of material. For example, the space between the first and thesecond major surfaces 905 a and 905 b can include materials having afirst refractive index and the space between the first and the secondmajor surfaces 905 a and 905 b can include materials can includematerials that have a different refractive index.

The one or more outcoupling optical coupling elements can include afirst optical coupling element 909 a and a second optical couplingelement 909 b, as depicted in FIG. 9B, which schematically illustratesan example of a cross-sectional view of the display device 900 along theaxis A-A′. In some embodiments, the first and the second outcouplingoptical elements 909 a and 909 b can be combined together to form asingle outcoupling optical element, e.g., on the same major surface oron both the first second major surfaces 905 a and 905 b.

The incoupling optical element 907 is configured to incouple incidentlight of a first plurality of wavelengths such that they propagatethrough the waveguide 905 by total internal reflection along a firstdirection and incouple light incident of one or more second wavelengthssuch that they propagate through the waveguide 905 by total internalreflection along a second direction. The first and the second directionsextend in a plane coplanar with the first or the second major surface905 a or 905 b of the waveguide 905. For example, as shown in FIG. 9A,when the waveguide 905 is viewed along a direction parallel to thesurface normal to the first or the second major surface 905 a or 905 b(e.g., as seen in a top-down view when the waveguide 905 is orientedwith the first major surface 905 a pointing upwards), the firstdirection can be parallel to the y-axis and the second direction can beparallel to the x-axis. Accordingly, FIG. 9A illustrates that the firstand the second directions are orthogonal to each other in a planecoplanar with the first or the second major surface 905 a or 905 b.However, in other embodiments, the first and the second directions canbe oriented with respect to each other at angles different from90-degrees when viewed along a direction parallel to the surface normalto the first or the second major surface 905 a or 905 b. For example,the first and the second directions can be oriented with respect to eachother at angles between about 60 degrees and 120 degrees, between about70 degrees and about 110 degrees, between about 80 degrees and about 100degrees, between about 85 degrees and about 95 degrees, or anglestherebetween. Preferably, the angle is chosen such that lightpropagating in the first direction is deflected at high efficiency byone of the outcoupling elements and low efficiency by the other of theoutcoupling optical elements, and light propagating in the seconddirection is deflected at high efficiency by the former outcouplingelement and low efficiency by the latter outcoupling optical element.

The one or more second wavelengths can be different from the firstplurality of wavelengths. In various embodiments, light having multiplecomponent colors (e.g., red, green, blue) can be coupled into thewaveguide. The first outcoupling optical element 909 a is configured toredirect, out of the waveguide 905, light of the first plurality ofwavelengths that propagate through the waveguide 905 along the firstdirection; and the second outcoupling optical element 909 b isconfigured to redirect, out of the waveguide 905, light of the one ormore second wavelengths that propagate through the waveguide 905 alongthe second direction. In some embodiments, the first plurality ofwavelengths encompasses light of two component colors, e.g., red andblue; and the one or more second wavelengths encompasses light of athird component color, e.g., green. Preferably, the two component colorshave a greater difference between the wavelengths of those two componentcolors than the difference between either of the two component colorsand the wavelength of the third color, which can facilitate reductionsin crosstalk. In some embodiments, the first outcoupling optical element909 a includes ASRs, which deflect light of each of the two componentcolors.

It will be appreciated that the waveguide 905 may be part of the stackof waveguides in the display system 1000 (FIG. 6). For example, thewaveguide 905 may correspond to one of the waveguides 182, 184, 186,188, 190, and the outcoupling optical elements 909 a and 909 b maycorrespond to the outcoupling optical elements 282, 284, 286, 288, 290of FIG. 6.

With continued reference to FIGS. 9A and 9B, in various embodiments, theincoupling optical element 907 can be a wavelength selective opticalcomponent that is configured to deflect different wavelengths of lightsuch that they propagate along different directions through thewaveguide 905 by TIR. For example, the incoupling optical element 907can comprise a first set of incoupling optical elements configured tointeract with light at the first plurality of wavelengths and a secondset of incoupling optical elements configured to interact with light atthe one or more second wavelengths. In various embodiments, the elementsforming the incoupling optical element 907 can include one or moreoptical prism, or optical components including one or more diffractiveelements and/or refractive elements.

In some embodiments, the incoupling optical element 907 can include oneor more gratings that can interact with light at one or morewavelengths. For example, if the incident light comprises light at red,green and blue wavelengths, then the incoupling optical element 907 caninclude a grating that interacts with all three wavelengths or a firstgrating that interacts with red light, a second grating that interactwith green light and a third grating that interacts with blue light. Insome embodiments, the first grating that interacts with red light andthe third grating that interacts with blue light can be combined in asingle grating structure. The one or more gratings included in theincoupling optical element 907 can include one or more of analog surfacerelief grating (ASR), Binary surface relief structures (BSR), VolumeHolographic Optical Elements (VHOE), Digital Surface Relief structuresand/or volume phase holographic material (e.g., holograms recorded involume phase holographic material), or switchable diffractive opticalelement (e.g., Polymer Dispersed Liquid Crystal (PDLC) grating). Othertypes of grating, holograms, and/or diffractive optical elements,providing the functionality disclosed herein, may also be used. The oneor more gratings are configured to direct incident light in the firstplurality of wavelengths—represented by rays 903 i 1 and 903 i 2—suchthat the light in the first plurality of wavelengths propagates throughthe waveguide 905 along the first direction (e.g., along a directionparallel to the y-axis) and direct incident light at the one or moresecond wavelengths—represented by ray 903 i 3—such that light at the oneor more second wavelengths propagates through the waveguide along thesecond direction (e.g., along a direction parallel to the x-axis).Accordingly, the one or more gratings are configured to couple lightinto the waveguide 905 by deflecting light incident from a directionforward of the first major surface 905 a or rearward of the second majorsurface 905 b at appropriate angles that results in the incident lightto undergo TIR in the waveguide 905. The incoupling optical element 907can include a reflective grating and/or transmissive grating. In someembodiments including one or more reflective gratings, incoming light isincident on the grating from within the waveguide 905 and is diffractedalong the first or the second directions of the waveguide 905.

In some embodiments, one or more wavelength selective filters 913 a and913 b may be integrated with or disposed adjacent to the incouplingoptical elements 907. The one or more wavelength selective filters 913 aand 913 b may be configured to filter out some portion of light at theone or more second wavelengths that may be propagating along the firstdirection and some portion of light at the first plurality ofwavelengths that may be propagating along the second directionrespectively. In some embodiments, the wavelength selective filters 913a and 913 b can be absorptive filters. For example, in variousembodiments, the wavelength selective filters 1013 a and 1013 b can becolor band absorbers.

In some embodiments, the wavelength selective filters 913 a and 913 bcan include a dichroic filter. FIG. 9C illustrates an example of adichroic wavelength selective filter 913 b and depicts the operation ofthat dichroic wavelength selective filter. The dichroic wavelengthselective filter 913 b (or 913 a) is configured to pass or transmitlight at the first plurality of wavelengths (or the one or more secondwavelengths) that is propagating along the second direction (or thefirst direction) by TIR and reflect the one or more second wavelengths(or the first plurality of wavelengths) propagating along the seconddirection (or the first direction) by TIR. The light that is passedthrough the dichroic wavelength selective filter 913 b (or 913 a) isabsorbed by an absorber 915 b that is integrated with or disposedadjacent to the dichroic wavelength selective filter 913 b (or 913 a).In this manner, the incoupling optical element 907 either individuallyor in combination with the wavelength selective filter 913 b (or 913 a)and absorber 915 b can increase the degree of isolation betweenincoupled light at the first plurality of wavelengths propagatingthrough the waveguide 905 along the first direction and incoupled lightat the one or more second wavelengths propagating through the waveguide905 along the second direction. In other words, the incoupling opticalelement 907 either individually or in combination with the wavelengthselective filter 913 b (or 913 a) and absorber 915 b can, by limitingthe amount of light of different wavelengths propagating through thewaveguide 905, reduce crosstalk between incoupled light at the firstplurality of wavelengths propagating through the waveguide 905 along thefirst direction and incoupled light at the one or more secondwavelengths propagating through the waveguide 905 along the seconddirection. Reducing crosstalk between incoupled light at the firstplurality of wavelengths propagating through the waveguide 905 along thefirst direction and incoupled light at the one or more secondwavelengths propagating through the waveguide 905 along the seconddirection can be advantageous in improving the outcoupling efficiency ofthe first and the second outcoupling optical elements 909 a and 909 band also improve the quality of the color image generated by theoutcoupled light.

The incoupling optical element 907 can be disposed adjacent the first orthe second major surface 905 a or 905 b of the waveguide 905. In variousembodiments, the incoupling optical element 907 can be disposed adjacenta corner of the waveguide 905. The incoupling optical element 907 can bedistinct from the waveguide 905. Alternately, the incoupling opticalelement 907 can be integrated with one or both of the first or thesecond major surface 905 a or 905 b of the waveguide 905. In variousembodiments, the incoupling optical element 907 and the waveguide 905can be monolithically integrated. In various embodiments, the incouplingoptical element 907 can be formed in a portion of the waveguide 905. Forexample, in embodiments, in which the incoupling optical element 907include one or more gratings, the one or more gratings may be formed ina portion of the first and/or the second major surface 905 a and/or 905b of the waveguide 905. In various embodiments, the incoupling opticalelement 907 may be disposed in a layer of optical transmissive materialwhich is disposed adjacent to the first and/or the second major surface905 a and/or 905 b of the waveguide 905. In some other embodiments, asdisclosed herein, the incoupling optical element 907 may be disposed inthe bulk of waveguide 905.

In various embodiments, the display device 900 can include first lightdistributing element 911 a disposed in the light path of the incoupledlight at the first plurality of wavelengths propagating through thewaveguide 905 along the first direction. The display device 900 can alsoinclude second light distributing element 911 b disposed in the lightpath of the incoupled light at the one or more second wavelengthspropagating through the waveguide 905 along the second direction. Thefirst and the second light distributing elements 911 a and 911 b can beconfigured to distribute light of the first plurality of wavelengths andof the one or more second wavelengths along the first and the seconddirection respectively. For example, in various embodiments, the firstand the second light distributing elements 911 a and 911 b can beconfigured to elongate light (e.g., spread light across the length) ofthe first plurality of wavelengths and of the one or more secondwavelengths along the first and second directions respectively. Thefirst and second light distributing elements 911 a and 911 b can bereferred to as pupil expanders or orthogonal pupil expanders (OPEs)since by virtue of distributing light along the first and the seconddirections, they can advantageously increase the spot size of a firstlight beam including light at the first plurality of wavelengths and asecond light beam including light at the one or more second wavelengths.The first and second light distributing elements 911 a and 911 b canalso be useful to increase the size of the exit pupil of the displaydevice 900. Increasing the size of the exit pupil can be useful when thedisplay device 900 is configured to be directly viewed by a user and/orin near-to-eye display applications. Increasing the size of the exitpupil can also be advantageous in alleviating the strain on eye whenviewing the display device 900.

The first and the second light distributing elements 911 a and 911 b caninclude one or more gratings that are configured to direct lightpropagating along the first and the second direction respectivelytowards the first and the second outcoupling optical elements 909 a and909 b. The one or more gratings can be configured, for example, to havea size (e.g., groove depth or groove height, shape, spacing, and/orperiodicity) and an orientation that is configured to interact withlight of the first plurality of wavelengths propagating along the firstdirection or light of the one or more second wavelengths propagatingalong the second direction. For example, if light of the first pluralityof wavelengths includes red and blue light, then the first lightdistributing element 911 a can include a grating that is configured tointeract with red and blue light or a first grating that interacts withred light and a second grating that interacts with blue light.Similarly, if light of the one or more second wavelengths includes greenlight, then the second light distributing element 911 b can include agrating that is configured to interact with green light.

In some embodiments, the first and the second light distributingelements 911 a and 911 b are each configured to redirect a portion ofthe light that impinges on the gratings at as the light every bounce asthe incoupled light at the first plurality of wavelengths and at the oneor more second wavelengths propagates through the waveguide by TIR. Thefirst and the second light distributing elements 911 a and 911 b candivide the first and the second light beams propagating along the firstand the second directions into multiple related beams that areredirected towards the first and the second outcoupling optical elements909 a and 909 b. In various embodiments, the multiple related beams canbe copies of each other. In this manner, the first and the second lightdistributing elements 911 a and 911 b can be configured to uniformly orsubstantially uniformly illuminate a larger area of the first and thesecond outcoupling optical elements 909 a and 909 b which can result ina fairly uniform pattern of exit emission from the waveguide 905.Without any loss of generality, the first and the second lightdistributing elements 911 a and 911 b can be configured to redirectlight incident at a single wavelength or multiple wavelengths within awavelength range.

In various embodiments, the one or more gratings included in the firstand the second light distributing elements 911 a and 911 b can includeone or more of an analog surface relief grating (ASR), Binary surfacerelief structures (B SR), a Volume Holographic Optical Element (VHOE),Digital Surface Relief structures and/or volume phase holographicmaterial, or a switchable diffractive optical element (e.g., PolymerDispersed Liquid Crystal (PDLC) grating). Other types of gratings,holograms, and/or diffractive optical elements, configured to providethe functionality disclosed herein, may also be used. The first and thesecond light distributing elements 911 a and 911 b can be disposedadjacent the first or the second major surface 905 a or 905 b of thewaveguide 905. In various embodiments, the first and the second lightdistributing elements 911 a and 911 b can be disposed such that they arespaced apart from the first and the outcoupling optical elements 909 aand 909 b, although the first and the second light distributing elements911 a and 911 b need not be so configured in some embodiments. The firstand the second light distributing elements 911 a and 911 b can beintegrated with one or both of the first or the second major surface 905a or 905 b of the waveguide 905. In various embodiments, the first andthe second light distributing elements 911 a and 911 b and the waveguide905 can be monolithically integrated. In various embodiments, the firstand the second light distributing elements 911 a and 911 b can be formedin a portion of the first and/or the second major surface 905 a and/or905 b of the waveguide 905. In various embodiments, the first and thesecond light distributing elements 911 a and 911 b may be disposed inone or more layers of optical transmissive material which are disposedadjacent to the first and/or the second major surface 905 a and/or 905 bof the waveguide 905. In some other embodiments, as disclosed herein,the first and the second light distributing elements 911 a and 911 b maybe disposed in the bulk of waveguide 905.

As discussed above, the first outcoupling optical element 909 a and thesecond outcoupling optical element 909 b are configured to redirectincoupled light that is incident on them out of the plane of thewaveguide 905. The first and the second outcoupling elements 909 a and909 b are configured to redirect the incoupled light that is incident onthe first and the second outcoupling elements 909 a and 909 b toward theviewer (e.g., eye 4, FIG. 7) at appropriate angles to ensure properoverlay of light at different wavelengths such that the viewer canperceive a color image of good visual quality. The first and the secondoutcoupling optical elements 909 a and 909 b can have an optical powerthat provides a divergence to the light that exits through the waveguide905 such that the image formed by the light that exits through thewaveguide 905 appears to originate from a certain depth. Accordingly,the waveguide 905 may be considered to have an associated depth planethat is correlated with the optical power of the first and the secondoutcoupling optical elements 909 a and 909 b. As discussed herein,various embodiments of display devices can include a plurality differentwaveguides similar to waveguide 905 described above—including theincoupling optical element 907 and the first and the second outcouplingoptical elements 909 a and 909 b with different optical powers—that arestacked together. In such embodiments, the different waveguides can beassociated with different depth planes corresponding to the differentoptical powers of the first and the second outcoupling optical elements909 a and 909 b including therein. Display devices including suchplurality of different waveguides stacked together can be useful togenerate 3D images and, in particular, light field based 3D images.

As discussed above, the first outcoupling optical element 909 a and thesecond outcoupling optical element 909 b can include one or moregratings. For example, the first outcoupling element 909 a can includeone or more gratings that are configured to interact with light of thefirst plurality of wavelengths and the second outcoupling element 909 bcan include one or more gratings that are configured to interact withlight of the one or more second wavelengths. For example, if the firstplurality of wavelengths includes red and blue wavelengths, then thefirst outcoupling element 909 a can include a grating structure thatinteracts with both red and blue light or a first grating that interactswith red light and a second grating that interacts with blue light. Asanother example, if the one or more second wavelengths includes greenwavelength, then the second outcoupling element 909 b can include agrating that interacts with green light.

The first and the second outcoupling elements 909 a and 909 b caninclude linear grooves that are configured such that light propagatingalong a direction substantially parallel to the length of grooves is notsufficiently deflected from its path such that it is couple out of thewaveguide. In contrast, light propagating along a direction that is atan angle with respect to the grooves (e.g., perpendicular to the lengthof the grooves) such that it impinges or strikes the grooves and isdeflected at angles that do not satisfy requirements for TIR and arethus coupled out of the waveguide 905. Accordingly, the grooves in thefirst outcoupling element 909 a are oriented along a direction parallelor substantially parallel to the second direction such that the light atthe one or more second wavelengths propagating along the seconddirection are not sufficiently deflected by the first outcouplingoptical element 909 a to be outcoupled out of the waveguide 905 andlight at the first plurality of wavelengths propagating along the firstdirection are sufficiently deflected by the first outcoupling opticalelement 909 a to be outcoupled out of the waveguide 905. The grooves inthe second outcoupling element 909 b are oriented along a directionparallel or substantially parallel to the first direction such that thelight at the first plurality of wavelengths propagating along the firstdirection are not sufficiently deflected by the second outcouplingoptical element 909 b to be outcoupled out of the waveguide 905 andlight of one or more second wavelengths propagating along the seconddirection is sufficiently deflected by the second outcoupling opticalelement 909 b to be outcoupled out of the waveguide 905.

The first outcoupling optical element 909 a and the second outcouplingoptical element 909 b can include analog surface relief grating (ASR),Binary surface relief structures (BSR), Volume Holographic OpticalElements (VHOE), Digital Surface Relief structures and/or volume phaseholographic material (e.g., holograms recorded in volume phaseholographic material), or switchable diffractive optical element (e.g.,Polymer Dispersed Liquid Crystal (PDLC) grating). Other types ofgratings, holograms, and/or diffractive optical elements, providing thefunctionality disclosed herein, may also be used. In variousembodiments, the first and the second outcoupling optical elements 909 aand 909 b can be integrated as a single outcoupling optical element 909.For example, a single outcoupling optical element 909 includingdifferent holograms for different wavelengths (e.g., red, green andblue) recorded on top of each other can be disposed on one of the majorsurfaces 905 a and 905 b instead of two outcoupling optical elements 909a and 909 b disposed on the first and the second major surface 905 a and905 b as shown in FIG. 9B. In some embodiments, the first outcouplingoptical element 909 a can be disposed on one of the first or the secondmajor surface 905 a or 905 b and the second outcoupling optical element909 b can be disposed on the other major surface. The first and thesecond outcoupling optical element 909 a and 909 b can be formed on oneor both of the first and the second major surface 905 a and 905 b. Invarious embodiments, the first and the second outcoupling element can beformed on a layer that is disposed on one of the first or the secondmajor surface 905 a or 905 b.

FIG. 10A schematically illustrates an example of a top view of a displaydevice 1000 including a waveguide 905, incoupling optical element 1007,wavelength selective filters 1013 a and 1013 b, and first and secondoutcoupling optical elements 1009 a and 1009 b. FIGS. 10B and 10Cillustrate examples of a cross-sectional view of the display device 1000depicted in FIG. 10A along the axis A-A′. The display device isconfigured such that incoming incident light of different wavelengthsrepresented by rays 903 i 1, 903 i 2 and 903 i 3 are coupled into thewaveguide 905 by the incoupling optical element 1007. The incouplingoptical element 1007 can be configured to couple all wavelengths of theincident light into the waveguide 905 at appropriate angles that supportpropagation through the waveguide by virtue of TIR. In variousembodiments, the incoupling optical element 1007 need not be configuredto incouple the different wavelengths of incident light such that theypropagate along different directions. Thus, in some embodiments, all thewavelengths of the incident light can be coupled into the waveguide 905such that they propagate through the waveguide along a same direction.The incoupling optical element can include a plurality of gratings, suchas, for example, analog surface relief grating (ASR), Binary surfacerelief structures (BSR), Volume Holographic Optical Elements (VHOE),Digital Surface Relief structures and/or volume phase holographicmaterial (e.g., holograms recorded in volume phase holographicmaterial), or switchable diffractive optical element (e.g., a PolymerDispersed Liquid Crystal (PDLC) grating). Other types of gratings,holograms, and/or diffractive optical elements, providing thefunctionality disclosed herein, may also be used. In variousembodiments, the incoupling optical element 1007 can include one or moreoptical prisms, or optical components including one or more diffractiveelements and/or refractive elements.

The display device 1000 includes wavelength selective filters 1013 a and1013 b, each wavelength selective filter 1013 a and 1013 b beingassociated with one of the outcoupling optical element 1009 a and 1009b. In the illustrated embodiment, wavelength selective filter 1013 a isassociated with outcoupling optical element 1009 a and wavelengthselective filter 1013 b is associated with outcoupling optical element1009 b. The wavelength selective filter 1013 a includes a first rearwardsurface and a first forward surface opposite the first rearward surface.The wavelength selective filter 1013 b includes a second rearwardsurface and a second forward surface opposite the second rearwardsurface. In some embodiments, the wavelength selective filter 1013 a canbe disposed on the first major surface of the waveguide 905, in arecess, e.g., such that the first forward surface is on the same levelas portions of the first major surface 905 a of the waveguide 905, asillustrated in FIG. 10B. In some other embodiments, the wavelengthselective filter 1013 a can be disposed such that the first rearwardsurface simply overlies the first major surface 905 a (without beingdisposed in a recess) as illustrated in FIG. 10C. In some embodiments,the wavelength selective filter 1013 b can be disposed in a recess inthe second major surface of the waveguide 905, e.g., such that thesecond forward surface is on the same level as the second major surface905 b of the waveguide 905 as illustrated in FIG. 10B. In some otherembodiments, the wavelength selective filter 1013 b can be disposed suchthat the second rearward surface simply underlies the second majorsurface 905 b (without being disposed in a recess) as illustrated inFIG. 10C. Light propagating in the waveguide 905 is incident on thefirst or the second rearward surface of the first or the secondwavelength selective filter 1013 a or 1013 b respectively. Light of thefirst plurality of wavelengths (or the one or more second wavelengths)are transmitted through the first rearward surface (or the secondrearward surface) of the first wavelength selective filter 1013 a (orthe second wavelength selective filter 1013 b). The first and the secondwavelength selective filter 1013 a and 1013 b are capable of reflectinga portion of the light transmitted through the first or the secondrearward surface.

The wavelength selective filter 1013 a is configured to transmit aportion of light at a first plurality of wavelengths (e.g., light at redand blue wavelength ranges) that are propagating through the waveguide905 by multiple reflections towards the respective outcoupling opticalelement 1009 a that are configured to deflect the first plurality ofwavelengths out of the waveguide 905. The wavelength selective filter1013 a is configured to reflect light at wavelengths different from thefirst plurality of wavelengths away from the outcoupling optical element1009 a. Similarly, the wavelength selective filter 1013 b is configuredto transmit a portion of light of one or more second wavelengths (e.g.,light in the green wavelength range) that are propagating through thewaveguide 905 by multiple reflections towards the respective outcouplingoptical element 1009 b that are configured to deflect light of the oneor more second wavelengths out of the waveguide 905. The wavelengthselective filter 1013 b is configured to reflect light at wavelengthsdifferent from the one or more second wavelengths away from theoutcoupling optical element 1009 b. In this manner, the wavelengthselective filters 1013 a and 1013 b can reduce crosstalk between thedifferent wavelengths of light that are coupled out of the waveguide 905to generate the color image.

In various embodiments, the wavelength selective filters 1013 a and 1013b can include one or more dichroic filters. The wavelength selectivefilters 1013 a and 1013 b can be disposed on the first and the secondmajor surfaces 905 a and 905 b of the waveguide 905. Without any loss ofgenerality, the wavelengths selective filters 1013 a and 1013 b can beconfigured to transmit light that is incident on the filters 1013 a and1013 b at near normal angles. For example, when the wavelength selectivefilters 1013 a and 1013 b are disposed parallel to the first and thesecond major surfaces 905 a and 905 b, light that is incident at anglesbetween, e.g., about 0 degrees and about 20 degrees with respect to anormal to the first and the second major surfaces 905 a and 905 b can betransmitted through the wavelength selective filters 1013 a and 1013 b.Accordingly, the wavelength selective filters 1013 a and 1013 b can beconfigured to transmit through light from the surrounding scene that isviewed by a viewer through the waveguide.

The first and the second outcoupling optical elements 1009 a and 1009 bcan be disposed on the corresponding wavelength selective filter 1013 aand 1013 b. For example, the first outcoupling optical element 1009 a isdisposed on the corresponding wavelength selective filter 1013 a andconfigured to outcouple light at the first plurality of wavelengths thatare transmitted through the wavelength selective filter 1013 a out ofthe waveguide 905. Similarly, the second outcoupling optical element1009 b are disposed on the corresponding wavelength selective filter1013 b and configured to outcouple light of the one or more secondwavelengths that are transmitted through the wavelength selective filter1013 b out of the waveguide 905. In some embodiments, as noted herein,the first plurality of wavelengths encompasses light of two componentcolors, e.g., red and blue; and the one or more second wavelengthsencompasses light of a third component color, e.g., green. Preferably,the two component colors have a greater difference between thewavelengths of those two component colors than the difference betweeneither of the two component colors and the wavelength of the thirdcolor, which can facilitate reductions in crosstalk. In someembodiments, the first outcoupling optical element 1009 a includes oneor more ASRs, which deflect light of each of the two component colorsand the second outcoupling optical element 1009 b includes ASR, whichdeflects light of the third component color.

It will be appreciated that the waveguide 905 may be part of the stackof waveguides in the display system 1000 (FIG. 6). For example, thewaveguide 905 may correspond to one of the waveguides 182, 184, 186,188, 190, and the outcoupling optical elements 1009 a, 1009 b andwavelength selective filter 1013 a, 1013 b may correspond to theoutcoupling optical elements 282, 284, 286, 288, 290 of FIG. 6.

The first and the second outcoupling optical elements 1009 a and 1009 bcan be physically and functionally similar to the first and the secondoutcoupling optical elements 909 a and 909 b described above withreference to FIGS. 9A and 9B. For example, the first and the secondoutcoupling optical elements 1009 a and 1009 b can include diffractivestructures, such as, for example, one or more of analog surface reliefgratings (ASR), Binary surface relief structures (BSR), VolumeHolographic Optical Elements (VHOE), Digital Surface Relief structuresand/or volume phase holographic material (e.g., holograms recorded involume phase holographic material), or switchable diffractive opticalelement (e.g., Polymer Dispersed Liquid Crystal (PDLC) grating).

Similar to the first outcoupling optical elements 909 a and the secondoutcoupling optical elements 909 b, first and second outcoupling opticalelement 1009 a and 1009 b are configured to redirect incoupled lightthat is incident on them out of the plane of the waveguide 905 atappropriate angles and efficiencies to facilitate or ensure properoverlay of light at different wavelengths such that a viewer canperceive a color image of good visual quality. The first and the secondoutcoupling optical elements 1009 a and 1009 b can have an optical powerthat provides a divergence to the light that exits through the waveguide905 such that the image formed by the light that exits through thewaveguide 905 appears to originate from a certain depth.

Light redistributing elements, such as, for example, first and secondlight distributing elements 1011 a and 1011 b can be disposed in theoptical path along which the different wavelengths of light propagatethrough the waveguide 905. The first and the second light distributingelements 1011 a and 1011 b can be physically and functionally similar tothe first and second light distributing elements 911 a and 911 bdescribed above with reference to FIGS. 9A and 9B. For example, thefirst and the second light distributing elements 1011 a and 1011 b caninclude diffractive structures, such as, for example, one or more ofanalog surface relief grating (ASR), Binary surface relief structures(BSR), Volume Holographic Optical Elements (VHOE), Digital SurfaceRelief structures and/or volume phase holographic material (e.g.,holograms recorded in volume phase holographic material), or switchablediffractive optical element (e.g., Polymer Dispersed Liquid Crystal(PDLC) grating). The first and the second light distributing elements1011 a and 1011 b can be configured to redirect a portion of the lightthat interacts with them as it propagates through the waveguide 905towards the first and the second outcoupling optical elements 1009 a and1009 b thereby enlarging the beam size of the interacting light alongthe direction of propagation. Accordingly, the first and the secondlight distributing elements 1011 a and 1011 b may be advantageous inenlarging the exit pupil of the display device 1000 including thewaveguide 905. In some embodiments, the first and the second lightdistributing elements 1011 a and 1011 b may thus function as orthogonalpupil expanders (OPE's).

Similar to the first and second light distributing elements 911 a and911 b, the first and the second light distributing elements 1011 a and1011 b can be disposed on one or both of the first and the second majorsurfaces 905 a and 905 b of the waveguide. In the embodiment illustratedin FIGS. 10A and 10B, the first light distributing elements 1011 a isdisposed on the first major surface 905 a and the second lightdistributing elements 1011 b is disposed on the second major surface 905b. In other embodiments, the first and the second light distributingelements 1011 a and 1011 b can be disposed on the same major surface ofthe waveguide 905. In various embodiments, the first and the secondlight distributing elements 1011 a and 1011 b can be combined to form asingle light distributing optical element.

In various embodiments, the first and the second light distributingelements 1011 a can be configured to be wavelength selective such thatthey have higher redirection efficiency for certain wavelengths of lightthan other wavelengths of light. For example, in various embodiments,the first light redistributing element 1011 a can be configured toredirect light at the first plurality of wavelengths towards the firstoutcoupling optical element 1009 a and the second light redistributingelement 1011 b can be configured to redirect light of the one or moresecond wavelengths towards the second outcoupling optical element 1009b. In such embodiments, the first light distributing element 1011 a canbe disposed over the first wavelength selective filter 1013 a and thesecond light distributing element 1011 b can be disposed over the secondwavelength selective filter 1013 b. In this manner, the amount of lightat the one or more second (or first plurality of) wavelengths that isredirected towards the first (or second) outcoupling optical element1009 a (or 1009 b) by the first (or second) light distributing elements1011 a (or 1011 b) can be reduced.

In the embodiments discussed above with reference to FIGS. 9A-10B, thefirst and the second outcoupling optical elements 909 a, 909 b, 1009 aand 1009 b can be configured to diffract light symmetrically on eitherside of the first or the second major surface that they are disposed onso that light from the waveguide is diffracted forward as well asrearward of the major surfaces 905 a and 905 b. Accordingly, the qualityof color image is not compromised even if some of the colors of thecolor image are output by outcoupling elements disposed on one majorsurface of the waveguide and some other colors of the color image aregenerated by light output by outcoupling elements disposed on the othermajor surface of the waveguide.

Additionally, the various incoupling and outcoupling optical elementsand the light distributing elements can be configured to interact withlight at a plurality of different wavelengths by combining differentsets of diffractive structures, each of the different sets ofdiffractive structures being configured to interact with light at asingle wavelength. The different sets of diffractive structures can bedisposed on the waveguide by using fabrication methods such as injectioncompression molding, UV replication or nano-imprinting of thediffractive structures.

With reference now to FIG. 11A, an example is illustrated of across-sectional side view of a plurality or set 1200 of stackedwaveguides that are each configured to output light of a differentwavelength or range of wavelengths. The set 1200 of stacked waveguidesincludes waveguides 1210, 1220, and 1230. Each waveguide includes anassociated incoupling optical element, with, e.g., incoupling opticalelement 1212 disposed on a major surface (e.g., a bottom major surface)of waveguide 1210, incoupling optical element 1224 disposed on a majorsurface (e.g., a bottom major surface) of waveguide 1220, and incouplingoptical element 1232 disposed on a major surface (e.g., a bottom majorsurface) of waveguide 1230. In some embodiments, one or more of theincoupling optical elements 1212, 1222, 1232 may be disposed on the topmajor surface of the respective waveguide 1210, 1220, 1230 (particularlywhere the one or more incoupling optical elements are transmissive,deflecting optical elements). Preferably, the incoupling opticalelements 1212, 1222, 1232 are disposed on the bottom major surface oftheir respective waveguide 1210, 1220, 1230 (or the top of the nextlower waveguide). In some embodiments, the incoupling optical elements1212, 1222, 1232 may be disposed in the body of the respective waveguide1210, 1220, 1230. Preferably, the incoupling optical elements 1212,1222, 1232 are color filters, including filters that selectively reflectone or more wavelengths of light, while transmitting other wavelengthsof light. Examples of colors filters include dichroic filters, asdiscussed herein. While illustrated on one side or corner of theirrespective waveguide 1210, 1220, 1230, it will be appreciated that theincoupling optical elements 1212, 1222, 1232 may be disposed in otherareas of their respective waveguide 1210, 1220, 1230 in someembodiments.

Each waveguide also includes associated light distributing elements,with, e.g., light distributing elements 1214 disposed on a major surface(e.g., a top major surface) of waveguide 1210, light distributingelements 1224 disposed on a major surface (e.g., a top major surface) ofwaveguide 1220, and light distributing elements 1234 disposed on a majorsurface (e.g., a top major surface) of waveguide 1230. In some otherembodiments, the light distributing elements 1214, 1224, 1234, may bedisposed on a bottom major surface of associated waveguides 1210, 1220,1230, respectively. In some other embodiments, the light distributingelements 1214, 1224, 1234, may be disposed on both top and bottom majorsurface of associated waveguides 1210, 1220, 1230, respectively; or thelight distributing elements 1214, 1224, 1234, may be disposed ondifferent ones of the top and bottom major surfaces in differentassociated waveguides 1210, 1220, 1230, respectively.

The waveguides 1210, 1220, 1230 may be spaced apart and separated by gasand/or solid layers of material. For example, as illustrated, layers1216 a and 1218 a may separate waveguides 1210 and 1220; and layers 1216b and 1218 b may separate waveguides 1220 and 1230. In some embodiments,the layers 1216 a and 1216 b are formed of materials that are indexedmatched with the materials forming the immediately adjacent one ofwaveguides 1210, 1220, 1230. Advantageously, the indexed matched layers1216 a and 1216 b may facilitate the propagation of light through thethickness of the set 1200 of waveguides, such that light can travel,e.g., through the waveguides 1210, 1220 and 1230 to the incouplingoptical element 1232 with little reflection or loss.

In some embodiments, the layers 1216 b and 1218 b are formed of lowrefractive index materials (that is, materials having a lower refractiveindex than the material forming the immediately adjacent one ofwaveguides 1210, 1220, 1230). Preferably, the refractive index of thematerial forming the layers 1216 b, 1218 b is 0.05 or more, or 0.10 ormore less than the refractive index of the material forming thewaveguides 1210, 1220, 1230. Advantageously, the lower refractive indexlayers 1216 b, 1218 b may function as cladding layers that facilitatetotal internal reflection (TIR) of light through the waveguides 1210,1220, 1230 (e.g., TIR between the top and bottom major surfaces of eachwaveguide). In some embodiments, the layers 1216 b, 1218 b are formed ofair. While not illustrated, it will be appreciated that the top andbottom of the illustrated set 1200 of waveguides may include immediatelyneighboring cladding layers.

Preferably, for ease of manufacturing and other considerations, thematerial forming the waveguides 1210, 1220, 1230 are similar or thesame, and the material forming the layers 1216 b, 1218 b are similar orthe same. In some embodiments, the material forming the waveguides 1210,1220, 1230 may be different between one or more waveguides, and/or thematerial forming the layers 1216 b, 1218 b may be different, while stillholding to the various refractive index relationships noted above.

With continued reference to FIG. 11A, light rays 1240, 1242, 1244 areincident on the set 1200 of waveguides. It will be appreciated that theset 1200 of waveguides may be part of the stack of waveguides in thedisplay system 1000 (FIG. 6). For example, the waveguides 1210, 1220,1230 may correspond to three of the waveguides 182, 184, 186, 188, 190,and the light rays 1240, 1242, 1244 may be injected into the waveguides1210, 1220, 1230 by one or more image injection devices 200, 202, 204,206, 208.

Preferably, the light rays 1240, 1242, 1244 have different properties,e.g., different wavelengths or ranges of wavelengths, which maycorrespond to different colors. The incoupling optical elements 1212,122, 1232 selectively deflect the light rays 1240, 1242, 1244 based upona particular feature of the property of light, while transmitting lightthat does not having that property or features. In some embodiments, theproperty of light is wavelength and the incoupling optical elements1212, 122, 1232 each selectively deflect one or more particularwavelengths of light, while transmitting other wavelengths to anunderlying waveguide and associated incoupling optical element.

For example, incoupling optical element 1212 may be configured toselectively deflect (e.g., reflect) ray 1240, which has a firstwavelength or range of wavelengths, while transmitting rays 1242 and1244, which have different second and third wavelengths or ranges ofwavelengths, respectively. The transmitted ray 1242 then impinges on andis deflected by the incoupling optical element 1222, which is configuredto selectively deflect (e.g., reflect) light of second wavelength orrange of wavelengths. The ray 1244 is transmitted by the incouplingoptical element 1222 and continues on to impinge on and be deflected bythe incoupling optical element 1232, which is configured to selectivelydeflect (e.g., reflect) light of third wavelength or range ofwavelengths. In some embodiments, the incoupling optical elements 1212,1222, 1232 are reflective color filters, such as dichroic filters.

With continued reference to FIG. 11A, the deflected light rays 1240,1242, 1244 are deflected so that they propagate through a correspondingwaveguide 1210, 1220, 1230; that is, the incoupling optical elements1212, 1222, 1232 of each waveguide deflects light into thatcorresponding waveguide 1210, 1220, 1230 to incouple light into thatcorresponding waveguide. The light rays 1240, 1242, 1244 are deflectedat angles that cause the light to propagate through the respectivewaveguide 1210, 1220, 1230 by TIR.

In some embodiments, to cause the light rays 1240, 1242, 1244 to impingeon the incoupling optical elements 1212, 1222, 1232 at the appropriateangles for TIR, an angle-modifying optical element 1260 may be providedto alter the angle at which the light rays 1240, 1242, 1244 strike theincoupling optical elements. For example, in some embodiments, the lightrays 1240, 1242, 1244 may be incident on the angle-modifying opticalelement 1260 at an angle normal to the waveguide 1210. Theangle-modifying optical element 1260 then changes the direction ofpropagation of the light rays 1240, 1242, 1244 so that they strike theincoupling optical elements 1212, 1222, 1232 at an angle of less than 90degrees relative to the surface of waveguide 1210. In some embodiments,the angle-modifying optical element 1260 is a grating. In some otherembodiments, the angle-modifying optical element 1260 is a prism.

With continued reference to FIG. 11A, the light rays 1240, 1242, 1244propagate through the respective waveguide 1210, 1220, 1230 by TIR untilimpinging on the waveguide's corresponding light distributing elements1214, 1224, 1234.

With reference now to FIG. 11B, an example of a perspective view of theplurality of stacked waveguides of FIG. 11A is illustrated. As notedabove, the incoupled light rays 1240, 1242, 1244, are deflected by theincoupling optical elements 1212, 1222, 1232, respectively, and thenpropagate by TIR within the waveguides 1210, 1220, 1230, respectively.The light rays 1240, 1242, 1244 then impinge on the light distributingelements 1214, 1224, 1234, respectively. The light distributing elements1214, 1224, 1234 deflect the light rays 1240, 1242, 1244 so that theypropagate towards the outcoupling optical elements 1250, 1252, 1254,respectively.

In some embodiments, the light distributing elements 1214, 1224, 1234are orthogonal pupil expanders (OPE's). In some embodiments, the OPE'sboth deflect or distribute light to the outcoupling optical elements1250, 1252, 1254 and also increase the beam or spot size of this lightas it propagates to the outcoupling optical elements. In someembodiments, e.g., where the beam size is already of a desired size, thelight distributing elements 1214, 1224, 1234 may be omitted and theincoupling optical elements 1212, 1222, 1232 may be configured todeflect light directly to the outcoupling optical elements 1250, 1252,1254. For example, with reference to FIG. 11A, the light distributingelements 1214, 1224, 1234 may be replaced with outcoupling opticalelements 1250, 1252, 1254, respectively, in some embodiments.

As disclosed herein, it will be appreciated that the outcoupling opticalelements 1250, 1252, 1254 may include diffractive structures, such as,for example, one or more of analog surface relief grating (ASR), Binarysurface relief structures (BSR), Volume Holographic Optical Elements(VHOE), Digital Surface Relief structures and/or volume phase holograms,or a switchable diffractive optical element (e.g., Polymer DispersedLiquid Crystal (PDLC) grating). In some embodiments, it will beappreciated that the outcoupling optical elements 1250, 1252, 1254 maybe three of the outcoupling optical elements 282, 284, 286, 288, 290 ofFIG. 6. In some embodiments, the outcoupling optical elements 1250,1252, 1254 are exit pupils (EP's) or exit pupil expanders (EPE's) thatdirect light in a viewer's eye 4 (FIG. 7).

Accordingly, with reference to FIGS. 11A and 11B, in some embodiments,the set 1200 of waveguides includes a separate waveguide 1210, 1220,1230; light distributing elements (e.g., OPE's) 1214, 1224, 1234; andoutcoupling optical elements (e.g., EP's) 1250, 1252, 1254 for eachcomponent color. The three waveguide 1210, 1220, 1230 may be stackedwith an air gap between each one, except where incoupling opticalelements (e.g., color filters) 1212, 1222, 1232 are located. The colorfilters reflect the desired color into its appropriate waveguide, whiletransmitting light of other colors. For example, light is initiallycoupled into the first waveguide 1210 by an angle-modifying opticalelement 1260, such as an in-coupling grating or a prism. The light isthen propagating at an angle which will result in TIR if the surface itencounters has a relative low refractive index material (e.g., air) onthe other side of the surface, or it will reflect almost entirely if ithits an incoupling optical element (e.g., color filter) 1212, 1222,1232, such as a properly designed dichroic filter when the light has theproper wavelength. In the example shown, light ray 1242 (e.g., greenlight) will reflect from the first incoupling optical element (e.g.,color filter) 1212, and then continue to bounce down the waveguide,interacting with the light distributing element (e.g., OPE's) 1214 andthen the outcoupling optical element (e.g., EPs) 1250, in a mannerdescribed earlier. The light rays 1242 and 1244 (e.g., blue and redlight) will pass through the incoupling optical element (e.g., colorfilter) 1212 and into the next waveguide 1220. Light ray 1242 willreflect from the next incoupling optical element (e.g., color filter)1222 and then bounce down the waveguide 1220 via TIR, proceeding on toits light distributing element (e.g., OPEs) 1224 and then theoutcoupling optical element (e.g., EP's) 1252. Finally, light rays 1244(e.g., red light) will pass through the incoupling optical element(e.g., color filter) 1232 and into its waveguide 1230, where itpropagates to its light distributing element (e.g., OPEs) 1234 and thenthe outcoupling optical element (e.g., EPs) 1254, finally coupling outto the viewer, along with the light from the other waveguides 1210,1220.

With reference now to FIGS. 12A-12B, examples of cross-sectional sideviews of a waveguide with an angle-modifying optical element 1260 tofacilitate the incoupling of light into the waveguide are shown. Asnoted herein, the angle-modifying optical element 1260 may includegratings that may, e.g., deflect light rays by diffraction. In someother embodiments, the angle-modifying optical element 1260 may be aprism, which may alter the direction or angle of propagation of lightrays, e.g., by refraction. FIG. 12A shows a wavelength band of lightbeing incoupled through the prism 1260 and reflected from the incouplingoptical element (e.g., color filter) 1212 and propagated by TIR withinthe first waveguide 1210. FIG. 12B shows a second wavelength band oflight being transmitted though the incoupling optical element (e.g.,color filter) 1212 and being reflected from the incoupling opticalelement (e.g., color filter) 1222 and propagated by TIR within thesecond waveguide 1220.

It has been found that the various waveguides (e.g., 905, FIGS. 9A-10B;and 1210, 1220, 1230, FIGS. 11A-11B) will benefit from being made usingmaterials having a high index of refraction. FIG. 13 is a plot showingthe expected impact of refractive index on field of view. FIG. 13illustrates simulation results from a single color eyepiece for thedisplay 62, the eyepiece being significantly similar to one of thewaveguides 1210, 1220, 1230 of FIGS. 11A-11B. In the simulation, theindex of refraction of the waveguide was varied up to values associatedwith various resins (at the high end), down to a value representingfused silica (at the low end). A clear increase in usable field of viewwas found and is shown in the graph. For this reason, in someembodiments, the various waveguides disclosed herein may be formed ofmaterial providing a high refractive index waveguide.

In some embodiments, the various waveguides disclosed herein (e.g., thewaveguide 905, FIGS. 9A-10C; and waveguides 1210, 1220, 1230, FIGS.11A-11B) may be formed of glass, polymer, plastic, sapphire, resins, orother materials that are transmissive to wavelengths in the visiblespectrum. As disclosed herein, waveguides comprising material withrelatively high refractive index can have a higher usable field of view(FoV). For example, the usable FoV can increase from about 35 degrees toabout 60 degrees when the refractive index of the material of thewaveguide increases from about 1.45 to about 1.75. Accordingly, variousembodiments described herein may include waveguides comprising materialwith a refractive index greater than 1.5, between about 1.5 and 1.8,greater than 1.6, or greater than 1.8.

In some embodiments, it will be appreciated that the waveguides withdiffractive structures (e.g., gratings) on the waveguides may be made,e.g., by injection compression molding, UV replication, ornano-imprinting of the diffractive structures on top of a high indexsubstrate. In some embodiments, such methods may be used to form eitherASR structure based designs or binary surface relief designs.

Various example embodiments of the invention are described herein.Reference is made to these examples in a non-limiting sense. They areprovided to illustrate more broadly applicable aspects of the invention.Various changes may be made to the invention described and equivalentsmay be substituted without departing from the true spirit and scope ofthe invention.

While illustrated as an eyewear in a wearable system as an advantageousexample, the waveguides and related structures and modules disclosedherein may be applied to form a non-wearable display. For example,rather than being accommodated in a wearable frame 64 (FIG. 2), thedisplay 62 may be attached to a stand, mount, or other structure thatsupports the display 62 and allows the display 62 to provide images to aviewer 60 without being worn by the viewer 60 (e.g., as a desk ortable-top monitor).

In some embodiments, various features described herein with reference tocertain figures may be utilized in embodiments discussed with referenceto other figures. For example, with reference to FIG. 9B, a color filtersuch as the color filters 1013 a, 1013 b of FIGS. 10B&10C, may beprovided between the outcoupling optical elements 909 a, 909 b,respectively, and the waveguide 905. Similarly, with reference to FIG.11A, a color filter similar to the colors filters 1013 a, 1013 b ofFIGS. 10B&10C, may be provided between the outcoupling optical elements1214, 1224, 1234 and their respectively waveguide 1210, 1220, 1230. Itwill be appreciated, that for each outcoupling optical element, thecolor filter separating that element from its corresponding waveguide isconfigured to transmit the wavelength or wavelength of light that theoutcoupling optical element is configured to outcouple, while reflectingother wavelengths of light.

In addition, many modifications may be made to adapt a particularsituation, material, composition of matter, process, process act(s) orstep(s) to the objective(s), spirit or scope of the present invention.Further, as will be appreciated by those with skill in the art that eachof the individual variations described and illustrated herein hasdiscrete components and features which may be readily separated from orcombined with the features of any of the other several embodimentswithout departing from the scope or spirit of the present inventions.All such modifications are intended to be within the scope of claimsassociated with this disclosure.

The invention includes methods that may be performed using the subjectdevices. The methods may comprise the act of providing such a suitabledevice. Such provision may be performed by the end user. In other words,the “providing” act merely requires the end user obtain, access,approach, position, set-up, activate, power-up or otherwise act toprovide the requisite device in the subject method. Methods recitedherein may be carried out in any order of the recited events which islogically possible, as well as in the recited order of events.

Example aspects of the invention, together with details regardingmaterial selection and manufacture have been set forth above. As forother details of the present invention, these may be appreciated inconnection with the above-referenced patents and publications as well asgenerally known or appreciated by those with skill in the art. The samemay hold true with respect to method-based aspects of the invention interms of additional acts as commonly or logically employed.

In addition, though the invention has been described in reference toseveral examples optionally incorporating various features, theinvention is not to be limited to that which is described or indicatedas contemplated with respect to each variation of the invention. Variouschanges may be made to the invention described and equivalents (whetherrecited herein or not included for the sake of some brevity) may besubstituted without departing from the true spirit and scope of theinvention. In addition, where a range of values is provided, it isunderstood that every intervening value, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention.

Also, it is contemplated that any optional feature of the inventivevariations described may be set forth and claimed independently, or incombination with any one or more of the features described herein.Reference to a singular item, includes the possibility that there areplural of the same items present. More specifically, as used herein andin claims associated hereto, the singular forms “a,” “an,” “said,” and“the” include plural referents unless the specifically stated otherwise.In other words, use of the articles allow for “at least one” of thesubject item in the description above as well as claims associated withthis disclosure. It is further noted that such claims may be drafted toexclude any optional element. As such, this statement is intended toserve as antecedent basis for use of such exclusive terminology as“solely,” “only” and the like in connection with the recitation of claimelements, or use of a “negative” limitation.

Without the use of such exclusive terminology, the term “comprising” inclaims associated with this disclosure shall allow for the inclusion ofany additional element-irrespective of whether a given number ofelements are enumerated in such claims, or the addition of a featurecould be regarded as transforming the nature of an element set forth insuch claims. Except as specifically defined herein, all technical andscientific terms used herein are to be given as broad a commonlyunderstood meaning as possible while maintaining claim validity.

The breadth of the present invention is not to be limited to theexamples provided and/or the subject specification, but rather only bythe scope of claim language associated with this disclosure.

What is claimed is:
 1. An optical system comprising: a waveguidecomprising a first major surface and a second major surface, thewaveguide configured to propagate light by total internal reflectionbetween the first and the second major surfaces; an incoupling opticalelement configured to incouple incident light into the waveguide at afirst plurality of wavelengths along a first direction and incoupleincident light into the waveguide at one or more second wavelengthsalong a second direction, as viewed in a top-down view of the waveguide,wherein incoupled light of the first plurality of wavelengths propagatethrough the waveguide along the first direction by total internalreflection and incoupled light of the one or more second wavelengthspropagate through the waveguide along the second direction by totalinternal reflection; and first and second outcoupling optical elementsconfigured to outcouple the incoupled light out of the waveguide.
 2. Theoptical system of claim 1, wherein the incoupling optical elementincludes one or more diffractive optical elements.
 3. The optical systemof claim 2, wherein the one or more diffractive optical elementscomprises one or more of an analog surface relief grating (ASR), abinary surface relief structure (B SR), a hologram, and a switchablediffractive optical element.
 4. The optical system of claim 3, whereinthe switchable diffractive optical element is a switchable PolymerDispersed Liquid Crystal (PDLC) grating.
 5. The optical system of claim1, further comprising: a first wavelength selective reflector configuredto reflect incoupled light of the first plurality of wavelengthspropagating along the first direction, while passing light ofwavelengths other than the first plurality of wavelengths; and a secondwavelength selective reflector configured to reflect incoupled light ofthe one or more second wavelengths propagating along the seconddirection, while passing light of wavelengths other than the one or moresecond wavelengths.
 6. The optical system of claim 5, furthercomprising: a first absorber configured to absorb incoupled lightpassing through the first wavelength selective reflector; and a secondabsorber configured to absorb incoupled light passing through the secondwavelength selective reflector.
 7. The optical system of claim 5,wherein the first and second wavelength selective reflectors aredichroic filters.
 8. The optical system of claim 1, wherein the light atthe first plurality of wavelengths includes red light and blue light. 9.The optical system of claim 1, wherein the light of the one or moresecond wavelengths includes green light.
 10. The optical system of claim1, further comprising: a first light distributing element configured toreceive incoupled light of the first plurality of wavelengths travelingalong the first direction and distribute the light of the firstplurality of wavelengths to the first outcoupling optical elements; anda second light distributing element configured to receive incoupledlight of the one or more second wavelengths traveling along the seconddirection and distribute the light in the second plurality ofwavelengths to the second outcoupling optical elements.
 11. The opticalsystem of claim 10, wherein the first and the second light distributingelements comprise one or more diffractive optical elements.
 12. Theoptical system of claim 11, wherein the one or more diffractive opticalelements comprise one or more gratings.
 13. The optical system of claim10, wherein the first light distributing element is configured toredirect light of the first plurality of wavelengths to propagate withinthe waveguide along a direction different from a direction in which thesecond light distributing element is configured to redirect light of thesecond plurality of wavelengths.
 14. The optical system of claim 13,wherein the first light distributing element is configured to redirectlight of the first plurality of wavelengths to propagate within thewaveguide along the second direction, and wherein the second lightdistributing element is configured to redirect light of the secondplurality of wavelengths to propagate within the waveguide along thefirst direction.
 15. The optical system of claim 10, wherein the firstand second light distributing elements are orthogonal pupil expanders.16. The optical system of claim 1, wherein the first outcoupling opticalelement comprises one or more gratings configured to outcouple light ofthe first plurality of wavelengths out of the waveguide; and wherein thesecond outcoupling optical element comprises one or more gratingsconfigured to outcouple light of the one or more second wavelengths outof the waveguide.
 17. The optical system of claim 16, wherein the one ormore gratings of the first outcoupling optical element are disposed onthe first major surface of the waveguide and the one or more gratings ofthe second outcoupling optical element are disposed on the second majorsurface of the waveguide.
 18. The optical system of claim 16, whereinthe one or more gratings of the first outcoupling optical element andthe one or more gratings of the second outcoupling optical element aredisposed on a same major surface of the waveguide.
 19. The opticalsystem of claim 16, wherein the one or more gratings of the firstoutcoupling optical element comprises one or more of an analog surfacerelief grating (ASR), a binary surface relief structure (BSR), ahologram, and a switchable diffractive optical element.
 20. The opticalsystem of claim 19, wherein the switchable diffractive optical elementcomprises a switchable Polymer Dispersed Liquid Crystal (PDLC) grating.